I had to review to remember this far back lol.
Spoilers below.....
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His mom is one of those parents that were so strict (and delusional herself) that it spilled into his warped personality. He's a momma's boy and they were basically trying to hunt for the perfect bride to become his mother-wife.
This was egged on by Osada's (big boobied lady) gossip around the office AND to Hayase to make it seem like Riko is begging him to marry her and that now they're engaged. She's using his delusions to get Riko out of the picture because it's obvious that Kano is interested in her. Osada can't stand the fact that she isn't the one being desired despite the effort she puts in to grab his attention.
Peak drama started when Hayase told the head guy that he and Riko were getting married, which everyone readily believed despite her protests (thinking it was a couple's spat) until Kano played her rejecting him on the loud speakers. Hayase gets suspended for sexual harassment.
Meanwhile, Osada is trying to butter up Hayase's mom, thinking she was Kano's mom because she saw the 2 of them chatting. She tells the mom that he's being 2 timed and she'll be a better match. Distraught, the mom agrees (remember, Hayase got his personality from his mom).
In the end though, Osada ends up being stalked by Hayase now, thinking she was helping him because she was in love with him. She's ran out of the company after being called out for being an office gossip who throws her work at others. They even labeled her "a perfect match for Hayase since they're both delusional."
Kano and Riko end up dating and discussing moving in together. The story then fades to the 3rd couple.

I wanna say... I read the next chapter and now I understand why he's crazy