
If there is a novel for it can you tell me where to read it and what chapter is it in the novel

If chapter 23 in manhwa, probably in chapter 77 in novel.
https://www.novelupdates.com/series/refusing-your-ex-husbands-obsession-a-guide/?pg=6#myTable

The art style is pretty but why does it has to become straight isn't he original a gay guy how did he turn to straight ╥﹏╥

Note that the blonde is craving for affection so when the fl said she loved him, his heart already set to not let go of that. It's not a matter of gay or bisexual but individual who shows him affection first. And for the step brother, it was said that he's obsessed and possessive so when the fl said she wanted to leave him, he doesn't like it cuz in his mind the fl would always be obsessed with him and not go for another so yeah...lol
I saw this on reels I saw the creator make a skit i never thought it will become a manhwa or manga(≧∀≦)