Season 1 ends with a gaiden: Shizu before Rimuru existed, a kingdom that wants a demon dead, and a black existence behind a pile of dead adventurers. Black and a mask is a character extra that plays like a horror job request.
Previous: Season 1 Episode 23 — Saved Souls · Hub: That Time I Got Reincarnated as a Slime
Hook
Season 1 ends with a gaiden: Shizu before Rimuru existed, a kingdom that wants a demon dead, and a black existence behind a pile of dead adventurers. Black and a mask is a character extra that plays like a horror job request.
This page is the sequential stop after Episode 23 — not a random recap dump. Scores below are for this 24 minutes only.
Quick Information
- Anime: That Time I Got Reincarnated as a Slime
- Season / Episode: Season 1, Episode 24 (overall #24)
- English title: Black and a Mask
- Japanese episode title: 外伝：黒と仮面
- Runtime: ~24 minutes
- Studio: 8bit
- Original air date: March 19, 2019
- Kagex score: 8.6 / 10
- Where to watch legally: Crunchyroll (region-dependent)
Should You Watch It?
Watch it if you like Shizu and want her at full adventurer power without the village tragedy. Episode 24 is a prequel side story, not Tempest plot. Skip it and you still understand Season 1’s main line — but you miss the best standalone Shizu hour and a demon who fights like a final boss in someone else’s story. Optional for lore, recommended for character.
Beginner-friendly? No as a start point. Watch from Season 1 Episode 1. This installment assumes you already know Tempest’s core cast — Rimuru at minimum.
Bottom line: sequential viewers should not skip “Black and a Mask.” Fight-only watchers may feel the talkier stretches; nation-building fans will not.
Spoiler Warning
Spoilers for Season 1 Episode 24 (“Black and a Mask”) follow. Stop above for a clean first watch. This page does not spoil later episodes.
Story Recap
A request with too many adventurers
Before Rimuru’s reincarnation, Shizue Izawa answers an urgent call to the Kingdom of Filtwood. The castle is already crowded with adventurers, which is the first wrong note. Jobs that need a crowd are either festivals or traps. Conqueror of Flames walking in with the anti-magic mask is the celebrity in a room of people who want the same bounty.
The request: a revived demon has been killing skilled adventurers by the handful. More than ten of the best already gone. Shizu takes work like this because that is who the hero’s student became — the person who shows up when the fire is other people’s problem.
Before Rimuru existed, Shizu walks into a castle already crowded with adventurers — first wrong note.
The job is not the job
Filtwood’s nobles want a demon subjugated. What they want under that is uglier: using adventurers as bait, politics, a summoned darkness they do not own. Shizu reads rooms as well as she reads fire. The episode’s middle is the realization that the castle is a stage and the demon is both the monster and the excuse.
Other adventurers die into the premise. That sounds cold. It is the point of a gaiden that wants Shizu isolated against something that kills “the best.” Her title has to mean something when the party is gone.
Nobles want a demon subjugated. Under that: bait, politics, a summoned darkness they do not own. Shizu reads rooms as well as fire. Castle as stage, demon as monster and excuse.
Black, interested
The demon in black — a primordial-class existence later generations will have other names for — is not a rampaging beast. He is curious. Shizu’s mask, her fire, her refusal to be a fun toy, register as interesting. Their fight is a conversation with lethal punctuation. She is at her peak as Conqueror of Flames. He is not fighting for a kingdom’s contract. He is sampling a human who might be worth remembering.
This is horror etiquette: the monster has manners and too much time. Shizu has a mask and a clock she does not know is already running on Ifrit. Two different immortalities scraping.
Primordial-class black existence, not a rampaging beast. Curious. Mask, fire, refusal to be a toy. Fight as conversation with lethal punctuation.
Flame versus a name that is a color
The duel is the budget: Ifrit-sourced fire against a demon who treats most adventurers as noise. Shizu does not win a clean fairy-tale kill. She survives being interesting. In a prequel, that is the only win available — she has to live long enough to meet a slime in Jura years later. The episode respects that without winking at Rimuru.
The mask is the visual thesis of the title. Black versus the covered face. A demon who is almost a concept fighting a woman who is almost a title. 8bit gets to draw Shizu as the lead instead of a tragic guest.
Ifrit-sourced fire against a demon who treats most adventurers as noise. No clean fairy-tale kill. She survives being interesting.
A story that will wait in someone else’s stomach
The gaiden closes without delivering Shizu to Tempest. It does not need to. You have seen the adventurer she was when she still had years. You have seen a black demon file her away as a memory. Season 1’s main line already taught you where she dies. This extra teaches you how large she was before that death.
As a finale, it is unusual: no Tempest founding, no Rimuru joke. As a character document, it is right. The season that began with a lonely slime ends by honoring the lonely human he inherited. Black and a mask. Then the credits, then years later a nation.
Does not deliver her to Tempest. Does not need to. You have seen the adventurer she was when she still had years.
Story Analysis
Episode 24 is a gutsy finale choice: a bottle prequel instead of a Tempest party. It will frustrate anyone who wanted a federation cliffhanger. It rewards anyone who thought Shizu was more than Rimuru’s face unlock. The Filtwood job as a trap, the demon as a connoisseur of strong humans, the mask as both armor and title — that is a complete short story. Placing it after Chloe’s miracle also lets Season 1 end on Shizu twice: once as a will completed, once as a life remembered.
Pacing is request, trap, duel, exit. Comedy is thin. World-building: primordial demons, noble summoning disasters, adventurer ecology in human kingdoms. Emotional impact depends on whether Episode 8 landed. If it did, watching her fight at full power is bittersweet in the correct way. If it did not, this is “why is the finale a side quest.” Fair split. I am on the bittersweet side.
Gutsy finale: bottle prequel instead of a Tempest party. Frustrates cliffhanger people. Rewards anyone who thought Shizu was more than a face unlock. Filtwood as trap, demon as connoisseur, mask as armor and title — complete short story. Placing it after Chloe’s miracle lets Season 1 end on Shizu twice: will completed, life remembered. If Episode 8 landed, watching her at full power is bittersweet correctly. If it did not, this is “why is the finale a side quest. ” Fair split. Bittersweet side for me. A Rimuru-free hour is the show insisting she had a legend before the slime. That insistence is the analysis.
Character Analysis
Shizue Izawa is the protagonist, full stop. The black demon is the guest boss: polite, lethal, curious. Filtwood’s nobles are the human trash of the week. Unnamed adventurers exist to die into her isolation.
Rimuru is not here, which is the point. No Benimaru, no Milim, no Gobta. If you miss them, you are the Season 1 audience being asked to sit with the woman whose face you got used to on a slime. The demon remembering Shizu is the character bridge the extra exists to build — without spelling the future.
Shizu is the protagonist, full stop. Black demon as guest boss: polite, lethal, curious. Filtwood nobles as human trash of the week. Unnamed adventurers exist to die into her isolation. Rimuru not here is the point. No Benimaru, no Milim, no Gobta. If you miss them, you are being asked to sit with the woman whose face you got used to on a slime. The demon remembering her is the bridge the extra exists to build without spelling futures. She is large. He is interested. That pairing is the whole cast that matters.
World Building
Human kingdoms can summon or revive demons and then hire adventurers to mop. Primordial-class demons treat most humans as uninteresting. Anti-magic masks and Conqueror of Flames as a peak otherworlder loadout. Adventurer parties as expendable policy tools.
Prequel timeline: this is the Western map before Tempest exists. No federation, no Gluttony, no Jura alliance. Just the old world’s monster-of-the-week economy, except the week’s monster is a color of the primordial. That scale gap is the lore. Shizu surviving it is the legend Rimuru later inherits as a face.
Human kingdoms can summon or revive demons then hire adventurers to mop. Primordial-class demons treat most humans as uninteresting. Anti-magic masks and Conqueror of Flames as peak otherworlder loadout. Adventurer parties as expendable policy tools. Prequel timeline: Western map before Tempest. No federation, no Gluttony, no Jura alliance. Old world’s monster-of-the-week economy, except the week’s monster is a color of the primordial. Scale gap is the lore.
Nothing here is later-arc homework. If a name or rule is only teased, it stays a tease.
Animation
Shizu-led action is the gift: fire, mask, a demon in black, castle architecture. 8bit treats it like a mini-movie inside TV limits. The duel has more extra frames than a random mid-cour fight. Adventurer deaths are quick and ugly. Finale-credit energy. Not Charybdis scale. Better character animation on Shizu than she got in the village weeks, which is the right allocation.
Shizu-led action is the gift: fire, mask, demon in black, castle architecture. Mini-movie inside TV limits. Duel has more extra frames than a random mid-cour fight.
Kagex animation score for this episode: 8.5 / 10 — peaks vs average cuts, not a sakuga clip ranking.
Music and Voice Acting
Score 8.4. 8bit’s TV mix leans on Elements Garden sting + silence. Japanese track is the reference for Rimuru’s dual register (cute slime vs office-brain). Dub timing varies by season; don’t wait on it to judge the episode.
Hidden Details
- Too many adventurers in one throne room is the tell the request is bait.
- The demon’s curiosity is more dangerous than a simple rampage because it files Shizu as a memory.
- A Rimuru-free finale is the show insisting Shizu had a whole legend before the slime.
Best Moments
- Shizu walking into a castle already full of people who will not walk out.
- Flame versus black, mask on, no slime jokes.
- The demon deciding she is interesting — the scariest compliment in the season.
Pros & Cons
Pros: Specific to “Black and a Mask” — A prequel finale that honors Shizu as a lead, not a face unlock. Optional for the war plot, recommended if Episode 8 meant anything to you.
Cons: Requires earlier episodes. Viewers who only want climax fights may call the political / logistics scenes slow even when they are load-bearing.
Final Verdict
Kagex overall: 8.6 / 10 — A prequel finale that honors Shizu as a lead, not a face unlock. Optional for the war plot, recommended if Episode 8 meant anything to you.
- Story: 8.5
- Characters: 9.0
- Animation: 8.5
- Music: 8.4
- Enjoyment: 8.6
I like this as a finale even when it throws people. Shizu getting a whole hour as the adventurer she was is the respect the death episode earned. The demon in black is ice-cold. See you in the nation-building season.
What to Expect Next
Season 2 opens on a busier Tempest, trade missions, and a slime whose calendar is now a national security document.
Next: Season 2 Episode 1 — Rimuru’s Busy Life. Watch legally on Crunchyroll.
FAQ
Do I need to watch Season 1 Episode 24?
Yes if you are watching the TV series in order. Skipping “Black and a Mask” leaves a hole later episodes assume you have.
What is the Japanese title?
外伝：黒と仮面 — Crunchyroll English title is “Black and a Mask.”
When did it air?
March 19, 2019 in Japan. ~24 minutes. Studio 8bit.
Is this Season 1 filler?
No. Tensura’s “quiet” hours are usually nation, diplomacy, or setup — not recap filler.
Where does this sit in the overall count?
Overall TV episode 24 of the main series (S1–S3 are 72; Season 4 continues from 73).
Should I watch Slime Diaries first?
No. Diaries is optional comedy. This review is the main TV track.
Where are character guides?
Tensura characters — Rimuru, Veldora, Milim, and the Tempest officers.
Where are facts / spoilers for the franchise?
Fact and Spoilers on the hub. This episode page stays inside Episode 24.
Keep exploring
- Tensura anime hub
- Season 1 review
- Overall review
- Previous: Season 1 Episode 23 — Saved Souls
- Next: Season 2 Episode 1 — Rimuru’s Busy Life
- Characters
- Fact and Spoilers
Your turn
Was “Black and a Mask” a continue episode or a skip-risk for you? Favorite beat? Who should get the next character page?
Sources: Crunchyroll episode titles; Wikipedia list of Tensura episodes; official Tensura anime site.
