I think meeting Mahito would be actually really endearing for Yuji even though they are bitter enemies, he's the only one who'll remain there to remind him of his past times and also in some sense, pact Yuji made with himself would be the only real purpose to keep living. If you actually think about it Yuji is in a really miserable situation now.
We often regret the things we didn't do, rather than the things we did
