Have you guys ever noticed that Pierrot courts the MC the exact same way he used to court Columbina, but with different intensities?
For example, in this scene, the Jester mentions that Pierrot used to give flowers of the valley to her. He also gives us a rose, but a handmade one, painted with Pierrot's own blood—something with a much deeper symbolism, showing a far greater level of devotion.
Pierrot was highly protective of Columbina against humans. He defended her and would get hurt by them as a punishment, but he kept protecting her anyway. With the MC, Pierrot shows himself to be even more protective, since he brutally kills the café customer just for being mean to the MC. From what we saw in the mirror, Pierrot wasn't that aggressive towards the humans who harassed Columbina.
He also used to hide his claws so he wouldn't scratch Columbina, just like he hides his monstrous nature now so he won't scare the MC
This proves that Pierrot’s love for Columbina was something more innocent, youthful—a classic first love. With the MC, however, it is an obsession; it’s something much more intense and deeply rooted. Of course, this is also due to what Pierrot went through. Back during Columbina's time, he had already experienced suffering, but he hadn't yet seen how truly cruel the world could be. That's why he was more innocent, younger, and more naive. By the time he meets the MC, he is much more experienced. He has learned how bad and cruel the world is, which is why he defends the MC in a much more intense and even violent way against anyone who slightly offends her. He will never let anyone hurt the person he loves ever again.
This is my first post, so please forgive me if it's bad or if there are any typos. English is not my first language.