The S.I.N. Phantom gives its protagonist an unusually personal qualification for exploring another realm. While the Netherworld damages other humans’ brains, your Mystic Yang Bloodline makes you immune—and gives you a role in treating its corruption through Dual Cultivation. You fight alongside female companions, deepen bonds through intimacy, and build a harem in a Cyber-Eastern setting where supernatural advancement and bedroom business share an agenda.
Ninth Studio pairs strategic team formations with character progression. Human and Yokai companions join you in battle as well as in the relationship story.
AI Opens a Very Different Kind of Portal
Humanity’s AI-assisted exploration of the universe brings about the Ghost Gate, a passage into the Netherworld and its unfamiliar entities. The discovery comes with a serious biological catch: a force field in that realm causes severe neurological damage. The condition is called S.I.N., short for Synaptic Instability Neuro-level, and goes by “Karmic Burden” in the underworld.
Your immunity protects you as the Crimson Moon spreads demonic corruption. It also makes you able to help those affected.
Dual Cultivation Does Double Duty
Dual Cultivation uses the protagonist's Pure Yang Essence to remove corruption and raise human companions' cultivation levels. Female Yokai seek it to balance their Yin energy.
Building relationships develops the harem while formations shape the combat team. Saving the realm comes with some unusual duties for this bloodline.
Animated CGs and a Necessary Content Note
The adult presentation includes animated CGs and full Japanese voice acting, alongside frequent explicit nudity and sexually suggestive dialogue. Training scenarios and the protagonist’s relationships with human and Yokai companions form part of that presentation.
Content note: Steam’s warning identifies non-consensual or coerced sexual interactions, as well as BDSM and role-playing content. It states that all characters are adults aged 20 or older.
Through the Gate on Windows
The S.I.N. Phantom launched on Steam on September 20, 2026, developed by Ninth Studio and published by EROLABS Publishing. It is available for Windows as a single-player, free-to-play game with in-app purchases.
More Screenshots
Images: © Ninth Studio / EROLABS Publishing
