Ranmaru has a tall and slender figure. He is pale-skinned, and has spiky silver hair. While it appears that he seems to have heterochromatic eyes (differently colored eyes), it has been confirmed that his true eye color is silver, and he uses a single purple contact for "aesthetic purposes". and his default outfit consists of a skin tight shirt with a houndstooth checkered vest.
He's a highly reactive and moody person, right into tsundere territory. He does however have a strong sense of duty. Ranmaru considers himself a rocker through and through and has his own ideals about what 'being a rocker' actually means and is actually fairly misogynistic in nature, refusing to work with Haruka because he wouldn't sing a song written by a girl. He stated that he didn't think anything but rock could speak to him after hearing ST☆RISH's song Maji LOVE 2000%.In All Star, it is revealed that the reason for this negative attitude is that the bands he was in in the past were all disbanded because of women as well as seeing the betrayal his dad went through with their family business. He has a lot of trust issues.
Ranmaru seems to not be completely negative, as is shown when he worked to help an elderly couple repay their debt to the Yakuza.
He likes to show-off and gives off the idea of feeling self-important, especially when he's performing.
Ranmaru doesn't get along with Camus (the two disagree quite often and end up fighting almost all the time), while Reiji pranks and picks on him. With his juniors, while Masato is easier for Ranmaru to deal with in regards to discipline, he is a bit more uncomfortable around Masato than Ren, who has a more laid back temperament. He shows a reluctant liking toward Cecil.
Like the other Shining idols, Ranmaru has an instrument: he plays bass guitar, and he's extremely fond of it, going so far as to call it the only girlfriend he needs.
His family was once a wealthy clan like the Jinguujis and the Hijirikawas, but his father was betrayed by a colleague and the family lost their fortune. The father worked himself to death, leaving the rest of the family with an immense debt, which Ranmaru took onto his shoulders. This led him to leave his family in hopes of becoming an idol, so he can settle the debt once and for all. He is slowly paying it back while he works to accomplish this. Ranmaru was a part of different bands before being signed on by Shining. He went through a few, but they always ended up disbanding, leaving him alone.
Ranmaru first appears with Camus, Mikaze Ai, and Kotobuki Reiji performing one of their songs as holograms,and ending as their human selves. Shining Saotome stated that the professionals would assist STARISH with their Master Course. Jinguji Ren and Hijirikawa Masato were assigned to work with Ranmaru. Ranmaru stated that STARISH wasn't anything special and they wouldn't make it far if they kept on relying on others. He continued, stating that he was only assisting STARISH because the president told them to. Hijirikawa protests, saying that they are not approaching half-heartedly.Jinguji then continues with Hijirikawa's statement, saying that they're prepared and they can beat his song. This provoked Ranmaru, as he asked Jinguji if he was trying to start a fight and to 'bring it on'. He is then calmed down by Kotobuki. Ranmaru then states that the pair do not seem like they have the will and he doesn't have any desire to teach them. Ranmaru,(as did all the other seniors,excluding Camus) took half of Hijirikawa and Jinguji's room and made them sleep in bunk beds.
In the game it is revealed that he, Masato and Ren were childhood friends because they were all "heirs to rich corporations". The Kurosaki Group went bankrupt after the father was betrayed and sold out, and Ranmaru never thinks back on it.
Ranmaru calls everyone by their first names. (same for Masato and Ren)
Unlike the other idols, Ranmaru's primary living place is a small, sparsely furnished apartment
He has an attachment to his bass, which he also calls as his "Girlfriend".
He is often flustered by Cecil's flattery.
He seems to show his softer side to cats, as he often feeds the strays in his neighborhood.
His heterochromia is not natural, it's just a purple contact with silver eyes as his natural pair.
His hair colour is also not natural. He has been dyeing it silver since he was a child.
Due to his tightly packed schedule, he has adapted to be able to fall asleep anywhere, anytime, and uses this ability to catch sleep during short breaks when he doesn't have work.