
Bestie, did we even read the same book??????? The girl he married clearly threatened him, not only with his family business, but with Touma's family business, he was trying to protect both of them, in a way that maybe you don't consider right, but the point remains. The girl threatened him to marry her.

Just in case you missed it, the girl's family was influential that she could threaten both his family and touma's. They lived in different era, their family had business which means they could not afford to bring their family down along with them as hayato said "if only i could've more prepared". Hayato admitted he was a coward, and there is a miscommunication in which the servant/maid also regretted that she became a spirit too. As for Hayato did not follow him in afterlife, if what you meant was Hayato not possessing the reincarnation as Yuuma did, I personally interpreted it as yes Hayato had regrets, but he died accepting the reality of them that can't be together in that era, yet he firmly believed they still mean for each other in another life, he also meant to give the amulet to Yuuma. That led to the present where Kaito and Yuuma meet each other and now Yuuma is the one giving Kaito the amulet.

They were gonna elope, whatever went on with the families wouldn't affect them themselves.
One also weights gains and loses, if there's no groom and he obviously doesn't take the family into consideration, what exactly are you threatening him with? The girl can say whatever she wants, is she the sole head of the family?
And the excuse was for Touma's sake? For his sake he wouldn't have been played like a fiddle by a girl. I agree, he was a coward and unprepared to the point of believing whatever was thrown at him.
So he married girl in another life, which became the reason past MC died, for the sake of the MC and I’m supposed to believe it? And after MC died Hayato didn’t even follow him in afterlife. It’s looks like Hayato just decided “welp I’m still gonna fuck this girl or whatever”. Like we didn’t even get his reaction at MC suicide, but we got couple hints he had a life with children. Did he even care? Nah this “for your sake” shit is propaganda I am not falling into. It’s one thing if ML is stupid and thinks he is protecting MC(from being poor? Whatever) but it’s absolutely disgusting to disguise his feelings as love if after MC died(because of ML betrayal), Hayato just kept living with his married life like it’s nothing. The story worked for me if Yuuma and Kaito were not reincarnations, but just being possessed or smth. Yuuma and Kaito were sweet, it’s such a pity they were stained that way. Anyway the main stuff was borrowed from this story(which is miles better) https://www.mangago.zone/read-manga/koi_no_yuurei/