I got the feeling that Norihiko set this situation up. He knew he was dying, he knew his brother was alone and miserable and, being twins, he also knew that if he could fall in love with the MC his brother would too. He was always saying he "knew because I am you and you are me." He also felt bad for the family always seeing his brother as a substitute, especially because Norihiko himself never did.
Norihiko hired the MC pretty randomly, which leads one to believe he'd been watching the MC for a while. If he sought out someone that he could love and have them return those feelings, the likelihood that the same would happen for his brother with that person were pretty high, in Norihiko's mind. And he was right.
I guess I also see it this way because it is something I'd do if I had a twin and knew I was dying.
Oh my god! I swear to god everyone should read your reply! What a great and positive explanation. Totally love it
Not too sure how to feel about this. Someone falling in love with their dead love's twin. But this kinda reminds me of a game I played where the MC's girlfriend's twin sister pretended to be her. She also ended up falling for the MC like the twin in this story. Though in that case, the twin sister was the only one who loved the MC. His real girlfriend didn't care. lol