[Guido]

So, until we get some answers as what or why it triggered on Yuuji to accept Serpent of the Altar, we can only entertain ourselves with some rich character insight memories or a very cool fight.

The fourth episode was packed with punch and serving twisted truths concerning Margery's obsession with the Silver.

Spoiler:

Hence, if I understood correctly Yuuji's explanations about the Silver's functionality, it became drawn to Margery's volatile and conflicting emotions; the ones she could never let out, and when Margery snapped the Silver killed everyone around her. It reflected back the resentment she held towards the people she met in her life, because Margery was sort of deceiving herself after experiencing bitter betrayal from others and still others came to rely on her.

Basically, Margery snapped because she felt she was only used and nobody loved her in return; that how she was feeling all those centuries.

Oh, yes... The letters which those pieces of plot devices became severely crippled and outshadowed in the transition from season two to this one.

Spoiler:

Maybe, Yuuji meant he was returning everything both Shana and Kazumi poured for him.

Maybe, Yuuji wishes to change the order of things or undoing meaning itself, because his inner world (the people he cares about and loves) is comprosed by how the universe functions: fate, burden, purpose of existence, and the why as to how and why everything works and is as it is.

Everything goes around and around and nothing is settled. Flames Hazes against Tomogara, and since the conception or dawn of meaning or to be nothing has settled down.