Chapter 130, where after spending most of Volume 12 being a massive Jerkass and being an abusive boyfriend to Aiko, Punpun gives a heartfelt speech and shows that he still loves her.
" I told you it's pointless talking about ifs and if nots. But...I do think it's nice if there could come a time where we could have fun talking about if and if nots, no matter how pointless it is...You know, I feel really happy right now. I'm so glad I was able to meet you in this life."
The fact that in the end, Punpun manages an Earn Your Happy Ending is incredibly heartwarming, and is a nice conclusion to such a cynical tale.