Not just a solid fan game, but a decent FPS all-around judging by the first level. The atmosphere and cutscenes are great, and the voicework, despite being A.I. generated (perhaps fittingly in this case) conveys the story well enough.
The enemy A.I. actually knows how to put up a fight and plays by its parameters consistently, so I never felt cheated when I died. They're just honestly good and I need to be at their level. The pacing of the encounters and story beats is also good, which is a rarity both in fan games and in full-scale FPS titles.
There are issues, namely the often uncontrollable recoil of both player characters' guns. Toning this down or making the bloom spread and directional kick more progressive would reward burst firing with increased accuracy
The lack of an ammo counter seriously hinders gameplay, as does the apparent lack of a dedicated crouch button. Some cover can't be fully utilized outside of slides (which to be fair are useful) and the rate of fire of these weapons means reloading is often poorly-timed.
This isn't such an issue in the first level since it's moreso an introduction setpiece, but if the game continues development and the challenges get more intense then this poses a serious problem. Movement mechanics such as vaulting are also quite abrupt and lack an organic flow, but this is obviously something that can be improved with time.
However, beyond basic bugs and the usual early-build rough edges, this is a fan game that seriously stands its ground. With more missions, enemies, story beats and basic polish, it could become one of the best fan games ever built around an anime.