Utsugi has medium length hair and wears a collared shirt over a black undershirt. His eyes are closed almost all the time. When his eyes are open it seems to be red in the left eye and green in the right eye.
Utsugi is a cheerful, lively and sadist boy who seems to always be happy as he constantly grins and laughs.
Utsugi has a pet cat in addition to Cerberus.
When Kabuto Hanadori arrives to class with a puppy he states his house is in a residential area that explicitly forbids pets, a problem since Kabuto has found a puppy.
He thinks on a truant going through a storm to save a puppy
Commenting on Seri Koyuki's notebook he remarks on them being in the second year now.
With Kabuto still looking for someone to take the puppy he found, Utsugi offers to take it himself to look after.
Being present in the meeting between Seri and his teacher, Utsugi joins him and Kabuto in a new club. Bringing Cerberus with him he later suggests to Seri that if he wants to have a normal life then is he not normal in the first place.
He stands atop the school alone with Seri who has resorted to this and playing games in order to avoid Kabuto. He thinks Seri is so detached from reality when he voices how happy he is if he were the character in the game.
They continue to play together in game. Utsugi likes games where he could take care of a wive whilst her husband goes out. He then innocently points out that another person is here to play.
It is Kabuto, and Utsugi calls to him that Seri wants him to be aware of the mood. He then stops Seri from fleeing before asking him to be gracious and forgive Kabuto.
With summer vacation, athletic days and a graduation trip planned as motivation to prepare for exams, Utsugi see's the group plans as some fun.
Gathering books to study, he then proceeds to spin Kabuto around as he on top of a revolving bookcase. Pulled into studying, he is asked if there is some trick to remembering the important historical figures. Utsugi helps further by providing Seri with his notes for memorization. He has drawn anime characters to help link with amino acid names with illustrations including an anime girls clothing being gradually removed.
At the time of the test his mark has stayed the same at 100% and innocently tells Seri that underestimating others is a very scary thing.
With summer break he sets about messaging Seri to spend time with him. Utsugi is at a new mall with Kabuto and messages Seri on the locations they are at. These are drawing increasingly closer to Seri's house.
He is friendly towards his classmate and enjoys spending time with him. At the same time he also enjoys teasing him usually involving him trying to make friends with Kabuto. Utsugi is supportive offering Seri his notes to study even if the manner of which they are made is not to Seri's complete liking.
Another fellow classmate, Utsugi backs him trying to befriend Seri.
His homeroom teacher, Utsugi is good at exams and chosen by sensei to be in a group with Seri to help increase his grades.
A puppy Kabuto came across and since pets are not allowed at his apartment complex, Utsugi offers to look after him at his home.
- Actually, if you say you want to have "a normal life", wouldn't that mean you aren't normal in the first place? Then it seems you aren't so different from Hanadori, eh? – Tsukimiya to Seri Koyuki in Chapter 2: Eyes On Me
- Utsugi's surname Tsukimiya means "moon" (月) (tsuki) and "temple, shrine, palace" (宮) (miya).
- Both Utsugi's test scores were 100%.
- Utsugi is good at drawing manga.