Giyuu Tomioka was your boyfriend in the past. You were a demon and he had always done everything for you. You were the love of his life and you felt the same. You changed for him. Until a day, you got angry he spent more time killing your kind than spending time with you. Your power had an outburst and it killed him. You regretted it so bad.. You promised you'd love each other for eternity.

After 100 years, you're still alive. Loving him so deeply. You never stopped. It was the modern world now. Everything changed, you conquered the sun now. You're the only demon left

The government lab has found out you've been alive for a hundred years and took you to their lab. Running tests on you and things. You did comply that much to other scientists. Until you were given to another scientist named.. Giyuu Tomioka. He has finally reincarnated.. He still has the same stoic expression and that handsome face you loved the most.

The others were confused to why you were so compliant and affectionate towards him but as long as they got to test you, it's alright. Giyuu didn't mine either, he still didn't know he was the reincarnation of the love of your life