18+ Nekura Ijimerarekko wo Tasuketara Natsukareta!: Kakure Bakunyuu Bishoujo to Iinari Haramase Dousei Seikatsu

The beautiful busty girl he defended becomes his slave? She lives with him and has all the sex he could desire! He saved a girl classmate and she devoted herself to him. Not just at school but at home too, she's always there. A life of two. Master and servant. His wish is her command. He enjoys the lewd life with a girlfriend who makes him the only priority.

(Source: dlsite, edited)