Romance where the MMC is scared to date as he worries he'll develop schizophrenia like his mother. Possible Spoiler.

[Ana]

I read this for free on Apple Books about 10ish? years ago, definitely over 5 years ago at least. I can't remember many details about the book itself but POSSIBLE SPOILER?

The second book begins with the MMC on a train going to or from work (possibly in Japan but I'm not 100% on that detail) when he all of a sudden thinks he's being chased by someone in black.