Solitude

In the au of Hagane no Samurai, the homunculi exist as obakemono, golems still but not of the same construct. One of the obakemono that Hagane meets early on is Ikari. Ikari is one of the obakemono that tow that faint like between darkness and light. He is the youngest of the obakemono, and Hagane intruiges him, so he follows after Hagane like a lost puppy.

Hagane is none too keen on that idea, but there's not much he can do aside from physically stop Ikari, and the obakemono has proved his worth in battle. Besides, he kind of reminds Hagane of his long-missing younger brother...