Mirai Sasaki

Sir Nighteye is a Pro Hero and Mirio Toogata's mentor. He is also a former sidekick of All Might.

Appearance
Sir Nighteye is a lean man with a well-kept appearance, wearing regular office clothes while on duty. He wears glasses and appears to be always glaring.

Personality
Sir Nighteye maintains a stoic and intimidating presence, with a cold and sharp glare, but that's only the side he shows in public. Nighteye actually greatly values humor and requires people to actually make him laugh first in order to acknowledge them.

History
Nighteye was once All Might's sidekick, however, they went through a fall out at some point in the past, and thus stopped working together.

After that, Nighteye started his own hero career, opening his own Hero Office. Mirio Toogata would devote himself in training under him for a whole year.

Synopsis
Sir Nighteye was first mentioned by Mirio and Gran Torino as a potential mentor for Izuku

He is first seen working on his computer in a dark room and being informed by Bubble Girl about the meeting between the League of Villains and Overhaul, the latter who is under investigation by Sir's organization.

All Might
Nighteye was once All Might's sidekick before their fall out. According to All Might, he feels rather awkward with the idea of meeting his former sidekick again because of a warning Nighteye gave him that All Might ended up becoming.

However, according to Mirio, Nighteye doesn't seem to hold any resentment or ill-will against All Might. Nighteye is said to be always watching All Might's videos.

Bubble Girl
She is Nighteye's sidekick and is the one who would inform him of any update information. She holds fear towards Nighteye if she fails to perform her tasks by his humourous standards.

Mirio Toogata
Mirio had been working under Nighteye for his internship for at least one year. Nighteye is the one who managed to improve Mirio's abilities and turning him into the number one student at U.A.

Mirio holds a deep respect for Nighteye and understands his mentor's behavior.

Quirk and Abilities
Sir Nighteye's hero tutoring skills are notable, as he managed to convert the then underachieving Mirio Toogata into a powerful hero student in less than a year.

Trivia

 * Nighteye's name and character could possibly be inspired by the DC Hero Dick Grayson, who was the former sidekick of Batman under the name Robin before parting ways with his mentor and donning his own hero name, Nightwing.
 * Nighteye's requirement to have people make him laugh at least once resembles the character King Kai from the Dragonball series.
 * Coincidentally, Nighteye's sidekick (Bubble Girl) has a closely similar name to the Dragonball character Bubbles, a monkey who lives with King Kai.