Cat

"Cat" is a stray cat that Prince Baka and Yukitaka take care of after nursing it back to health, making it's debut in Chapter 1 and Episode 1 respectively.

History
After running out into the night, Yukitaka catches up to Baka in the park to see that he's injured lying against a tree, holding a cat claiming to have saved it. It's unclear as to how the cat (and Baka) were harmed, but Baka is able to heal the gravest of their injuries using his self regenerative properties. The cat has resided in Yukitaka's apartment since then, occasionally seen with Miho Edogawa when he's away.

Trivia

 * Prince Baka had rigged a security camera to the cat unbeknownst to Yukitaka, Miho and his subordinates as part of his "grand plan", as revealed in Chapter 3/Episode 3.