Third girl is an unnamed uma appearing in Obey's flashbacks. She's based on the American racehorse Sunshine Forever, though JP fans call her Emu or Emu Moto (moto = original). Apparently because Obey "emulates" her mannerisms?

Anyway, this particular fan artist likes shipping her with Obey a lot.

These four girls' designs really do confirm the open secret that, yes, Kuzumi-sensei likes his girls muscular with big titties and ass.

Jnglmpera said:

These four girls' designs really do confirm the open secret that, yes, Kuzumi-sensei likes his girls muscular with big titties and ass.

And all six feet tall or taller.