Presumably because he has black unit stats, reduces the cost of all dark knights by 2, increases the durration of their skills by 30% and his own skill will halve the attack of enemies while active.
Well, then do I have some good news for you. The current DMM event seems to star 3 new male units (two plats and a silver). So whenever the devs get around to translating it you'll have your wish.
That said, I seem to recall reading that the all ages versions of the female scenes also gave lore and background info, though we don't exactly have that in the Nutaku version.