Clavis

Clavis appears as young man who is almost always smiling and keeping his eyes closed. He has spiky green hair with a streak of yellow color on the left side of his bangs. In the back, a red side cut is visible on both sides of his head. He also has piercings on his right ear and nose.

His uniform consists of a light brown blazer-like coat with dark brown collar and cuffs atop a white shirt and red tie. Additionally, his coat has two columns of yellow buttons, and yellow hemlines patterned before the cuff and a pin on the left side of his collar. He wears gloves, brown pants and a pair of black leather shoes.

Clavis is mysterious and formal but always acts amiably and serves with a smile. He enjoys a good drink, goofing around and teasing others when the time is right.

Clavis has usually only short appearances, mostly transporting Nona and others between floors.

After Nona breaks up the fight between Ginti and Decim, he teases Ginti and takes the puppet used to test Decim with him, telling Decim that the rest of the day is off.

He is a guest at the mini concert held by Harada and Mayu Arita, and is visibly enjoying it.

Clavis gets his memories read by Oculus after the later suspects Nona of hiding something from him. He is dismissed immediately after, unaware of what happend.

At the request of Decim, Clavis takes him and the black-haired woman to the lowest level, where the used dummies are disposed and which is only accessible after Clavis inserts a special key and a new button becomes visible. Later he visits Ginti in the Viginti, asking about Memine and, after learning she disappeared, for a drink.

Nona

The two are on friendly terms and Nona trust him as he is one of the few people aware that Decim is an arbiter with human emotions. Clavis serves as her extremely loyal valet.

Decim

The two seem to have a good relationship, greeting each other politely and are friendly to each other.

Ginti

Clavis has a more complicated relationship with Ginti appreciating and teasing him, but also staying by his side when Memine disappeared.

• Clavis is the Latin word for "key".