#so much of Owner's motivation is revealed to be about what Sasaki cares about and has cared about over his various lives

[iztarshi]

I think Phantom Tales of the Night has the most varied monsters I've seen in a manga. Not physically, but in the way they think, so that even the monsters themselves can struggle to understand one another.

Spoilers ahead, because figuring out how these monsters think and what they're doing and even which people are monsters is a lot of the manga's mystery.

You've got Butterfly, very young by monster standards and with his youth extended by his recurrent amnesia, who is born from a collection of lost human souls although he's not human himself. Even the older monsters trying to parent him don't really know what he is or what he should be so their attempts to guide him into "growing up" can hinder him as much as help.

Bone Monk is blunt and practical. He only wants to gather the bones of the dead and make them into pottery, which might seem morbid but seems genuinely to be born of compassion. As Owner puts it he gathers up the broken and discarded.

Spider used to be human and although he thinks differently after hundreds of years he's still human at base.

The Foxes are malicious and careless, gambling for humans in order to steal their skins and lives only to discard them when they get bored. But we also meet a Tanuki who takes the skin of a dead human out of compassion in order to raise her daughter instead of leaving the child an orphan, so Beasts are not always like that.

Sasaki, as a being who can regenerate from a single bone again and again into a half-skeletal man, is probably a true-born monster and was never human at all. But he thinks exactly like a human, and a compassionate and level-headed human at that, which leads to him trying to spend lifetimes among humans. He understands humans the way they'd understand each other, but always feels he's hiding a terrible secret.

Owner, as a formless creature of darkness, is revealed to have probably had good intentions in the end but his approach to problem solving is so alien that that "probably" remains. He only gave himself a face and identity so Sasaki (after one offer to be friends with him made as a tiny bone) would be able to find him again and it remains his nature to be ambiguous. The blurred line between monstrous curiosity, wanting to learn how humans act in circumstances he sets up including cruel ones, and strange ways of helping, which often include letting humans blame him if it would be easier than blaming other humans or themselves, always lingers.