Akame Nisei (赤目二世)
Quite a mysterious character. He first appeared in volume 5, masquerading as Seimei and visiting Misaki to drug her with pills and encourage her to kill Ritsuka. The plan didn't work, but Nisei just moved on to wiretapping the Aoyagi house. When Soubi discovered him, he also discovered that Seimei had moved on to a new fighter, and Nisei just reveled in Soubi's despair. Nisei's unrelenting cruelty and delight in others' pain is similar to the personalities of the boy Zeros.
In volume 7, Nisei has a 2-on-1 fight with Soubi and Ritsuka, and he reveals a marking on his hand that says 'BELOVED'. The origins of this marking have not yet been revealed. Perhaps it was new, or perhaps he was just very skilled at concealing it, and there's still the unanswered question of why he has it. Alas, it's yet another unanswered question.