Honestly, I'm impressed with artistic choices, but the art director of Infinity Nikki definitely deserved his role!

It's Unreal Engine 5 and RTX Accelerated version of Lumen lighting system.

There is even their official interview about switching to Unreal Engine: https://www.unrealengine.com/en-US/developer-interviews/behind-the-scenes-of-infinity-nikki-tracing-a-glamorous-turn-to-an-unreal-open-world

The trick is: they haven't just adopted the engine, their rendering developers recreated lots of features, like Order-Independent Transparency (OIT). Imagine, that folks can do rendering in a gacha about dresses, but AAA games are all using the default UE.

#ArtDirection@GameDEV
#LevelArt@GameDEV
#UnrealEngine@GameDEV