Reviewed work by NEKOUJI · View on DLsite
Cyan Brain is a bleak, gore-soaked sci-fi side-scrolling action-shooter in which a memoryless heroine fights her way through a ruined city of machines, and every defeat cashes out as a dedicated execution animation. It’s built for players who want their adult content welded to genuinely demanding ryona action rather than bolted onto a token combat shell. If random blood splatter, broken-armor defeat scenes, and a decadent horror atmosphere are deal-breakers for you, this isn’t your work and that’s fine.
What works
The action is the real spine here, and it holds up. This is a Unity-built 2D side-scroller with a recoil system, so different firearms carry different weight, power, and knockback against enemies, and the game leans into that with twenty-nine enemy and trap types plus rideable battlefield weapons to deploy. The difficulty is no joke — the community consensus is that it’s hardcore and punishing, and the game topped the doujin sales charts in its first week on the strength of the action alone. That’s worth stressing, because a lot of h-action games coast on the porn and phone in the gameplay; this one would survive as a straight shooter even with the erotic layer stripped out.
Presentation is the other clear strength. Each enemy type gets its own unique 2D defeat animation, blood spatters land randomly and convincingly, and the mix of 2D foreground with 3D stage backgrounds gives the ruined-cathedral-and-machinery setting real mood. The full named voice cast — four credited performers across the protagonist, the lost Church hunter HS202, the former nun L, and the mysterious M — sells the portentous story dialogue, and the memory-fragment progression gives you a reason to keep pushing past each brutal encounter. The framing of violence and salvation, church bells and bodily collapse, is genuinely atmospheric.
On the h-system itself, the integration is smart. Being defeated by a monster triggers a matching execution animation, and you collect a “death card” afterward, which turns losing into a deliberate completionist loop. Better still, your outfit takes progressive damage as you get hit during normal play, so there’s a continuous strip-tease running through combat instead of payoff only at the game-over screen. A gallery lets you revisit everything you’ve unlocked.
What doesn’t
The adult content is narrower than the feature list implies. Total animation runtime is around twenty-five minutes, spread across roughly a dozen-and-a-half short H animations, a couple of dynamic recollection scenes, and a small handful of static CG. Almost all of it is monster-on-heroine defeat content — interspecies, machine, and insect partners, with the expected grotesque and ryona bent. The recollections are the only real exception, leaning into a yuri pairing that shifts in a futa direction. There’s no consensual or romance angle anywhere, so if game-over erotica isn’t your thing, there is genuinely nothing here for you.
The bigger letdown is the audio mismatch. Story dialogue is fully voiced, and combat has hit-reaction voice work, but the H animations themselves play silent. For a work this polished elsewhere, unvoiced erotic scenes feel like a real omission and noticeably flatten them. There’s also an inherent friction in the design: the scenes are gated behind defeat, but the game is hard and combat-heavy, so players who came mainly for the porn have to either grind through punishing action or throw matches on purpose against enemies that don’t make dying easy. And while the atmosphere is a plus, the narrative tips into opacity — long on doom-laden “existence and annihilation” mood, short on actually explaining what’s happening.
Who should buy this
English text is supported, so non-Japanese readers can navigate the menus, systems, and story without a fan patch — and since the erotic animations are wordless anyway, you lose nothing there. Buy this if you want a hard, gory action-shooter first and ryona-style adult content second, and you’re specifically into monster, machine, and insect defeat scenes with progressive armor destruction. Steer clear if you want vanilla or voiced h-scenes, a large CG count, or a low-effort gallery to unlock without fighting for it.
Verdict
7.5 / 10 — an accomplished, genuinely punishing action-shooter with standout gore-horror atmosphere, held back for adult-content buyers by a limited and frustratingly unvoiced scene set.
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