Probably is gonna be that but like it's such a dumbass plan if it is he really doesn't have to do all that. Past life him was better Ladidida
From what I seen it’s half/half. He’s no longer loyal to her due to his feelings. His feelings twisted as our FL grew, which will show more later in the chapters.
The blonde guy literally sacrifices his life for FL and the way he act, seems like he have his own plan.
Sure it cost FL trust and betrayal. But we can see the blonde guy will be one of the "Man's" in chapter 1
The cliche plan- make fl n lily hate and distrust him, so he can make sure fl n lily will be safe in the future.
Since he know her brother is a pyscho, so he need to be close to the pyscho himself to know what his planning.
Cliche but oh well. If it work, it works.