Mayu has short black hair and eyes that are colored green. She usually wears a white kimono with red hakama. During the time she worked with Yato, she wore a dark red kimono with light purple vertical stripes and a pink scarf around her shoulders.
As Tenjin’s weapon, she transforms into a smoking pipe. However, when she worked as Yato's weapon, she transformed into a dagger and was only used during battles.
Mayu has a very honest personality and a strong sense of justice. During the time she worked for Yato, she couldn’t stand his attitude. Not only did he constantly laze around, but he also often talked about killing and didn’t seem to care about humans that needed his help. Because of this she complained a lot and always insulted and badmouthed Yato after she quit.
Despite her attitude towards Yato, she also respects Yato and cares for him. She often gets worried whenever Yato got into trouble even when she is serving Tenjin. At one point she volunteered herself to help Yato, who was impure due to Yukine’s actions.
Despite not being a Stray, Mayu has two known names:
- As Yato’s former shinki, her name was Tomo (伴, meaning “partner”), her human name was Tomone (伴音). Her vessel name was Han, and as an item, her name was Hanki (伴器). She transformed into a dagger. This name was revoked by Yato due to her decision to quit being his shinki; however, Yato still calls her Tomone despite her protests.
- As Tenjin’s shinki, her name is Makoto (真, meaning “pure”), and her human name is Mayu. Her vessel name is yet to be announced in the manga, however, it is assumed to be Shin, and as an item, she transforms into a pipe. This is her current name.
Mayu has three known abilities, namely Boundary, Zan (斬, rend; lit. "slay"), and Zetsu (絶, sunder; lit. "sever"). Boundary is a basic skill she has as a shinki, while Zan and Zetsu, were skills only attainable during the time she belonged to Yato. She is yet to show any skills as Tenjin’s shinki.
- She obtains this skill when she becomes a god’s shinki. She is only able to use this skill in human form. In the manga and the anime, she uses this skill together with Daikoku and Kazuma to perform the purification ritual towards Yukine in chapter 11 of the manga and episode 9 of the anime.
- Zan / Rend
- She obtains this skill in her weapon form Hanki, only when used by Yato. When Yato uses Zan, she is able to slay and exterminate a phantom. She uses this skill to kill phantoms that linger around Mutsumi’s school in episode 1 of the anime and chapter 1 of the manga. In the manga, this skill is never named.
- Zetsu / Sunder
- She obtains this skill in her weapon form Hanki, only when used by Yato. When Yato uses Zetsu, she is able to sever the bonds between a human and things / other people that cause harm to him/her. She uses this skill to sever the bonds between Mutsumi and her classmates, and cause Mutsumi's classmates to treat her as a stranger. This skill is shown in chapter 1 of the manga, but is never animated. This skill is also never named in the manga.
- Mayu's true name, 真 makoto, means "truth" or "reality".
- The character added to make her given name, 喩 yu, means "metaphor".
- Unlike most shinki, the archaic version of the kanji used for Mayu's name that adorns her person, 眞, is not entirely obsolete and still sees limited use in given names.
- She seems to dislike people with suicidal tendencies.
- She is afraid of large fires. Possibly because of how she died, as a human.