特捜天使シェルセイバー

Main character Yuichi is a university student who lives a normal life till he gets fatally wounded by the criminal organization “Duon” executive confronting Space Sheriff Shellsaver. However, he manages to survive through assimilation with the reinforced clothing provided by Space Sheriff. Shellsaver loses a huge portion of her power through this act, so Yuichi swears to make up for his salvation. Two heroes of justice will fight side by side!

[From vndbreview]