Nighteye wasn't always that strict. He was one of All Might's biggest fans,admired him,and became his sidekick for until 6 years. During his battle against All For One,he got critical injuries. Nighteye begged All Might to retire and told him to look for a One For All successor at the U.A School,particularly Mirio Togata. After their dispute,they went their separate ways. Even if we know Nighteye's strict and cold personality,he actually do in fact have a soft side and values humor. He believes that a world without smiles and humor has no bright future. The point of him is that he was designed and meant to represent the intention of invoking the stereotypical image of Japanese men. That's why he was so strict,cold and had authority. Despite All Might choosing Deku as his successor instead of Mirio,he wasn't that happy,since Deku was Quirkless when All Might found him. By the time,Nighteye didn't know that a Quirkless person was required. He's quick and very open whenever he would make mistakes. Nighteye became very fearful of his own Quirk,scared of any visions he would see,pretty much made him paranoid. He soon met Mirio and took him under his wing. He became his pride and joy. Nighteye was a special person to Mirio. He wasn't just a mentor to him. He was the one who managed to improve Mirio's abilities and turned him into the number one studant at the U.A. At first,Nighteye only saw Mirio as the most suitable candidate to replace All Might,but during the time he was training him for that role,he learned that Mirio holds a deep respect and admiration for him and understands his behavior,becoming his most treasured student. During the Shie Hassaikai raid,he hugs his seriously-injured pupil after rescuing and protecting Eri from Overhaul. A proud Sir Nighteye praises and congratulates Mirio for everything that he has done,but is devastated to learn that Mirio had lost his Quirk when he was hit by a Quirk-Destroying bullet while protecting Eri. Nighteye literally tried to protect Mirio,Deku and Eri until he got badly hit. And you think he's being a dickhead? You don't even know how much respect and honor Sir Nighteye is. He's a true hero. If you don't think he is and that he's an assole,screw you. You don't know what a real hero like him is. In the hospital,Mirio rushes into the room to plea to him to hold on to teach him more,reminding him that he only became strong thanks to his help and training. Nighteye comforts Mirio,using his Quirk one final time to see into his future. Sir Nighteye passes away peacefully and smiling,after assuring Mirio that he will become an outstanding hero. That's when Mirio burst out crying. Pretty much later on,Nighteye received a funeral. That shows how much he got respect from everyone. Later on as well during the School Festival when Class A was doing their performance and Eri started smiling for the first time,not only was Mirio felt happy about it,he claims if only Nighteye was there to see this,with tears falling down on him. Nighteye's death truly was impactful. I remember crying my head off uncontrollably when it happened and I still cry even nowadays. I also used to dislike his strict attitude at first when he first debuted,but when I found out he truly is a real hero and sacrificed himself to save not just his student,but Deku and Eri as well,I started crying and he has deserved my whole respect. So when he died,a part of me also died. We know what they say,it's better to learn on who someone really is before judging them. Thanks to Nighteye's courage,I learned to take care of myself and to continue on not giving up no matter how hard life gets. He's my hero and always will be.