@Astraea Forgive her for something she didn't do, like I said. If you want me to lay the thought process out...
1. Cecil never met Eugene since he left to see the noble house.
2. She never got to hear from him personally when she was told he was breaking off the engagement.
3. She got sick and died before seeing how anything else played out.
Therefore, Cecil doesn't know what exactly happened or why Eugene left her. Following so far? Next:
1. Keefa acts like Cecil did something wrong.
2. He mentions treasuring both their current lives.
3. He doesn't get why she's so angry at him.
Therefore, Keefa's understanding of what happened in their past life is very different from Cecil's. Furthermore, Eugene's life after he and Cecil parted ways wasn't necessarily pleasant either.
This either means that Eugene doesn't know the full story of what happened either, or he somehow twisted the truth in his own head to delude himself. If it's the latter, then he's an idiot and the logic train ends here. If it's the former:
1. Lizz doesn't fully know what happened in her previous life.
2. Keefa doesn't fully know what happened his previous life.
3. All nobility so far have been shown to be arrogant assholes that think nothing of commoners.
4. Cecil and Eugene were both living as commoners up until the incident.
5. Keefa assumes that Lizz doesn't want to see him.
Therefore, it's a likely possibility that Eugene's noble house lied to both of them to split them up for their own convenience and Eugene was told that Cecil did something akin to abandoning him. Again, assuming this is the case and he isn't just super twisted by nature:
1. Keefa sees his former lover in this new life.
2. He assumes Cecil abandoned him because of lies he was told in the past.
3. He says he wants things to just be water under the bridge and hopes for the two of them to live separate but happy lives.
In conclusion, he feels wronged by her, but wants to prioritize their current lives. And so, he's trying to "forgive" her for whatever wrong he was told she did in their past life so they can both live in peace.
Did that clarify things?