From Taichi's narration, it's not because of guilt that they broke up. Remember they broke up after two years of relationship, most high school relationship ended up - it's normal, because they will meet more people after leave school. And he come in terms with Touma, probably something happened when they meet again.
This story shows how relationships are complicated and real. Touma and Taichi didn't happened just because of guilt and friendship. It was genuine and true. It was more than that.
I thought Taichi felt guilty from his pov in chapter 53, when he mentions he couldn't bring himself to see Futaba and when he talks with Futaba 'again' about the future he wanted to choose. When he said 'again', I interpreted it as he had already mentioned to her about his feelings for Touma (here I was also guessing that this was during his and Futaba's relationship). There's also the ambiguous part where he says 'to come to terms with it for good', this can really be interpreted in so many ways (ie: ending his relationship with Futaba, coming to terms with wanting a future with Touma, etc.)
Also I didn't say that Taichi and Touma's relationship happened because of guilt, I meant that Taichi had guilt because he realized his romantic feelings for Touma during his relationship with Futaba. Also, I feel like the author gave a lot up for interpretation considering that we really don't get a lot of information of how things ended the way that they did so how you and I interpret the ending may be completely different.
What I'm trying to say is that Taichi and Futaba's break up didn't came from Taichi 's guilt of not really loving her. He did loved her. She loved him too. That's why they were both blushed when Taichi shouted "I Love You" when they were at the see. That Tachi and Touma's end game didn't happened because of that guilt Taichi had with Futaba.
It was genuine, it just happened. Him and the girl just didn't worked out. That is life. It's normal. They realized that they are not meant to be.
I think it's enough to know that Taichi and Touma ended up together, that this is their "Happiness". The specific details doesn't really matter on how they started talking again or how they started these feelings. I feel like we should know even without knowing.
I know that Taichi and Futaba genuinely liked each other, I didn't say that they didn't, we know that it was true because of the conversation with Touma and Futaba's friends' husband talking about how their partners can like both men and women. And I do understand that things could just not have simply worked out between them but I just thought that the author hinted that something more happened with touma's pov. The specific details matter to me at least as a reader, I'm sure alot of people wanted to know more and have a better understanding of what happened considering the fact that we never saw Taichi explicitly show romantic interest in Touna until the timeskip.
A shame, but I think there were (barely) enough crumbs for us to imagine what it was like.
If it had I think one or two timeskips before this, I think it couldv'e solved stuff.
I'm disappointed that the author didn't show more of how Taichi and Touma's relationship progressed. How did Taichi figure out that he loved Touma romantically? Was this part of a reason of why he and Futaba broke up? Im guessing it is because it seems like Taichi felt guilty towards Futaba, maybe he realized his feelings too late in their relationship and knew he had to make the choice to leave?I wanted to see more romance scenes between Touma and Taichi but I know that the author didn't intend for this to be a love story so that's probably why. Sad we couldnt see future Touma either side note, I'm glad to see Seiya with his 3 kids and wife, I'm sure he's a great father