In My Hero Academia, more than a few characters need a personal hero to look up to, and that ranges from Izuku and Ochaco to Tamaki Amajiki of the "Big Three."
Although he is grouped with the mighty Mirio Togata and Nejire Hado at the pinnacle of U.A.'s studentry, Tamaki Amajiki has a humble origin. He was born lacking confidence and belief in himself at first. In a number of ways, he actually mirrors Izuku Midoriya, and in that same vein, Mirio Togata is much like All Might himself.
Finding The Sun
Tamaki didn't have a good start to his heroic career. As a boy in third grade, he suffered horrible shyness and had trouble even introducing himself to his new classmates. He also noted that no one wanted to approach him or make friends with him, and he was sure that he'd just be a plant withering in the shade. This was not the recipe for a future hero. But then, one of his classmates did approach him: a certain Mirio Togata. Mirio was sure that the shy, stuttering Tamaki wanted to say "I'll become a hero," and at once, Mirio bonded with Tamaki over that. Tamaki was in awe that this radiant boy was shining like the sun. Mirio was warm and strong, unlike Tamaki.
Tamaki was bewildered but he didn't dare reject Mirio's friendship offer. Instead, Mirio became Tamaki's personal hero, and he could finally open up and be a more confident and likable version of himself. And it worked: Mirio thought that Tamaki was way cool, and by middle school, he was telling Tamaki to believe in himself and not hide from the world any longer. Tamaki has incredible potential and must recognize it before he can nurture it. Mirio, meanwhile, played down his own abilities and potential so Tamaki wouldn't be so intimidated. This would pay off later.
What Tamaki Must Do
Every hero needs a name, and Tamaki realized that his mission was to surpass his personal savior Mirio and become something more. Mirio said that even the sun can be eclipsed, and Tamaki resolved that he would "eat" it and become #1. And so, he became Suneater, the hero who can overcome all challenges.
This is related to Izuku's own quest to top All Might and become the next symbol of peace. Like Tamaki, Izuku started from a low point; lower, in fact, since he had no Quirk at all. But he did have a hero, All Might, and he soon met his hero one fateful afternoon. All Might, like Mirio a few years prior, took himself down a few pegs and decided to entrust the future of heroism to Izuku rather than himself. All Might was ready to pass the torch, and he needed Izuku to "eat" the legend of All Might and replace him as a symbol.
Mirio and All Might both act according to the core tenet of being a hero: putting others first. Even at the cost of self-sacrifice or losing everything. Even Stain the "Hero Killer" will agree that a true hero never acts for personal glory, but instead, to lift others up and bring out their potential. A hero is not only a defender, but a nurturer, and that was what Mirio was to Tamaki and All Might was to Izuku. But it's up to Izuku and Tamaki to seize that opportunity with great courage and conviction, or else those sacrifices were in vain.
Tamaki was a bud that must now blossom magnificently, and it wouldn't have been possible without the sun shining on him.