SPOILER-
so first off you'll meet the ml the next storyline. He travels through each world just like her however unlike her his memories get wiped each time. He has a vague feeling of familiarity but can't actually remember who she is. He's the worst agent in his system because her missions always clash with his. He should have been kicked out of this own agent system but his stepbrother is the big boss of the system or something so he continues to be there despite sucking at it horribly. He's incredibly arrogant too and narcissistic (especially about his mission; he refuses to acknowledge his inability to fulfill them)but around the mc, he's pretty helpless. The mc has no idea that all the men she got close to each world were the same person for a while and he didn't recognize her for a while either. Later on, he'll use a memory retainer thingy or something that will hypnotize him into remembering her every time he leaves the world, after courting her for many many transmigration trips she'll finally accept his love for her.
I might have messed up/if you want to get more spoiled here are the links
novel link- https://lightnovelheaven.com/series/coming-of-the-villain-boss/
spoiler link- https://forum.novelupdates.com/threads/fast-wear-system-villain-boss-struck.65284/
I don't think that the first two men had him in them tbh. He had to leave the body once it got ruined so there was no way for him to stay there in the first dude's body. And we can clearly read about the fact that it's not the original host's soul in the body so I think both the schoolboy and the adopted dude were the real ones.

Can anyone spoil me if she ever gets with anyone? Cause i really just want her to stay single and badass. She don't need no man nor woman in her life. She just needs emergency food!