I think it was done mostly in Nanase’s POV, but we got glances into Leo’s POV and it’s just as painful, he just had to deal with his feelings differently because he had duties to an entire kingdom. Leo never moved on, he’s just living a lie and as he said every day the burden grows, and him going into bed with his wife while silently crying is proof. He was one straw from breaking and running away. I’m sure if Nanase took him away he wouldn’t fight it, but they both thought the world of each other and wanted the other to live the “best” life. More evident in the flashback to Leo remembering their promise, that if he ever push Nanase away and hide it with a smile, Nanase should know that it’s a lie and he wants to be with him forever. The fact that their past lives ended in tragedy and no promises of reincarnation but Leo’s soul practically chased after Nanase so they could meet again is proof that his love was in fact just as deep
Damn, Nanase really got the biggest middle finger in his past life. The man he loved married and had a kid, gained power and became the king. All the while Nanase kept drowning in his own feelings, unable to move on.
It also doesn't help that Leo's yearning post-marriage really was NOT captured well at all. It looked like he had already moved on from Nanase and only Nanase continued to love Leo. The author seriously should have focused on Leo's yearning post-marriage more for it to be believable that he still loved Nanase in the new life. As it stands, it doesn't look like he held the same feelings as Nanase by the end of their past lives. Leo's past self's feelings deserved more expansion.
Their grown up past selves are SO good-looking. It was such a missed opportunity to never use those designs for their present selves. They looked fucking majestic as hell. This deserves a sequel with those designs and this time focusing more on Leo's feelings about his actions in his past life.