Deceased virus patient has their soul isekai-ed in Terra, of the Arknights Fandom. However, instead of reincarnating into the numerous sub-species, the world has to offer, his soul gets tied to a specific shard of raw Originium. The result is a super cancer crystalline-spirit hybrid, capable of hijacking the body of anyone who comes into contact with one of their Originium shards...after the infection reaches the late stages.

Overall, our MC is just plainly tired of body-hopping and wants it to stop.