Wow that ending is... so unbelievably disappointing. Actually, I guess the right word would be unsatisfactory.
It seems like Kyuu's relationship with Ai is a total trainwreck after their break-up. It doesn't even seem like they keep up with each other anymore with the "She's gotten pretty." line. Her character is so sad that just thinking about it makes me cry. She lost the chance to make her childhood friend her partner because of a robot that was impossible to be partners with. Imagine waiting for that long, only to realize that he's chasing a love that CAN'T HAPPEN. Kyuu fumbled SO HARD it's actually insane.
I don't think you understand how incredibly frustrated I am at the reunion too. After seeing that Ichiko really did forget everything, the least he could do was try and move on at least. There should at least be SOME kind of win in here? Right? Nope, he goes for seconds. He's really going to repeat the same tragic shit that happened in the past, just for the CHANCE that Ichiko will be with him. Mind you, that version of Ichiko practically DIED that day, as he says. HE KNOWS there is no way they will ever be reunited. He goes back in anyway.
Combine the fact that his relationship with Ai is much worse than before, the fact that Kyuu is still stuck in the past, and the fact that nothing has changed for robots. What you get is a set of characters I love that got completely shitty endings. It's legitimately hard to move on because it's so frustrating what could have been.
Maybe that is the point? Don't chase things that are impossible to catch? I don't know anymore. I would still recommend reading it, not like the every other chapter is invalidated by this ending.