Why

Well, I think Tsukki is overthinking. LDR is kinda hard and there's a possiblity that Kuroo and Tsukki will fall out of love (not all lovers fall out of love, but some are). If I were Tsukki, I will give it a try then if its not working for both of us, I will make a decision right away.

Like with what the person said above lol
Did you skip through parts of it?
Tsukishima was overthinking and then Kuro being in college and being busy made him overthink even more and they broke up
So ig yeah, if I were tsukishima I would've done the same thing, since you could see he was overthinking, if I was also overthinking the same thing I'd want to break up as well

Yo, I can totally relate with Tsukki in this story.
Because I also did it.
But I never wanted to get back together with the guy though..

At the time we were far from each other,
I really thought that he's much better off with someone near him than being in a LDR.
It's much better that I or he won't think about things that I or he will be with someone behind my/his back, so it's better to just break up.

So yeah, I did broke up with the guy because I can't handle LDR.
Just sharing... ╮(￣▽￣)╭

I wholly agree with the above responses lmao LDR are difficult and it only gets more difficult when you’re left stewing up all the negative thoughts (in kei’s case)— really, it might just seem like breaking up is inevitable in the end.

Adding the fact that Tsukki was in highschool, he's hasty in making decisions and thought that was the best course of action since the feelings' been bothering him plus he thought all he and Kuroo did was meet-up and have sex which doesn't count as a relationship really.
But then Kuroo being really into him and was loyal had given them another chance at it so all ends well (▰˘◡˘▰)