Unfair of him to not give the seme the option to cut the string by hiding the fact that it had connected.
Because he knows the seme would choose to cut the string. The seme wants to be with him and would never choose the girl. Him not letting the seme cut it means you now have a third party involved who can’t find a new soulmate because hers in already in a relationship that he wouldn’t choose to leave. Not cutting the string also means that her string doesn’t get to reattach to someone else. Therefore she doesn’t get to have a new fated person. Therefore it is unfair to her.
I liked this a lot, but it also made me incredibly angry. I get his thought process of not telling him that the string was connected, he wanted him to have some one if it didn't work out. BUT it was very unfair to not give him the opportunity to choose and also unfair to the girl, because even if Hara and Kaoru did work out she wouldn't have the opportunity to find a new soulmate. I also hate when characters self sacrifice out of doubt in their relationship, themselves, and because they feel like they don't deserve happiness. I have been in that position too many times to count and it angers me to see.