Black Star! ★

Black☆Star appears as a teenage, young man with bright, blue spiky hair with the spikes sticking in out in the manner similar to that of a star. He's also somewhat short, being shorter than his weapon partner Tsubaki Nakatsukasa. He's also well built for his age. He has green eyes and when under the effect of Madness or angered, his eyes adopt blue stars within them.[19]

His main outfit consists of a sleeveless black shirt with a funnel-like collar, with white trousers that are black from the knee down and just a little short of being full length jeans. On the front of his collar, two short strips of grey material adorned with rivets stretch down from the top of the collar to the breast of his shirt. Black☆Star has similar strips wrapped around his neck in the form of a scarf, and around his waist in the form of a belt. Rivets can also be seen on his pockets and on the ends of his trousers. On his hand, he wears gray fingerless gloves with heavy wrist weights and has a band going across the back of each hand, adorned with a star. Black☆Star's footwear are basic black boots with white tips, with a star shape visible on the toe of each boot. On his right shoulder is his star-shaped tattoo, showing his heritage as a member of the Star Clan which is just a shade lighter than his normal skin tone.

An assassin with an unusual trait of desiring to be in the spotlight, Black☆Star can be described as a wild meister in contrast to his calmer weapon partner with dreams of "transcending the gods". Eventually, Black☆Star also develops the goal of committing himself to mastering the Path of the Warrior.

Initially, Black☆Star was remarked to be intensely self-centered by Stein, causing him to not take certain situations seriously and his arrogance causing him to to be narcissistic and is visibly riled by those who he believes has or is wanting to attention away from himself.