Arc I, Chapter 1

After being killed in a traffic accident, Duo wakes up in a medieval fantasy novel - except he's woken up as one of the novel's minor villains who was supposed to have died in a main character's backstory. Intent on righting the wrongs of his novel counterpart, Duo sets out to change his fate and just maybe improve the relationship between himself and his estranged husband, Duke Heero Yuy.

(Duo is isekai'd into the body of a novel's villainess character and runs with it.)