MONSTER EATER

Rude, an E-rank adventurer. His only skill, "Status Ailment Nullification," is a niche ability considered useful only for gathering medicinal herbs in miasma-choked dungeons. With virtually zero combat prowess, his fellow adventurers mock him with the nickname "Miasma Scavenger." In a desperate bid to change his life, Rude ventures into a new dungeon—only to be betrayed by his party and left for dead. With his supplies gone and his life fading, he makes a forbidden choice: to consume the flesh of a monster. So begins the tale of Rude’s "Monster Devouring" adventure, where he gains new skills by simply consuming his foes! (Source: Ani-One Asia) — Description from AniList community (anilist.co).