Yamaguchi tadashi.

As a child, Yamaguchi was bullied by boys in his class who told him he was ugly. Nobody defended him, nobody was on his side, and he had no friends, until a tall boy helped him. But even with a friend, he lived in his only friend's shadow and became very insecure, since girls only pursued him because of his best friend Tsukishima, who was the most handsome boy at Karasuno. But one day he met a beautiful girl with the brightest blue eyes in the world and unique hair, white as snow, and skin as pale as silk. Yamaguchi immediately fell in love with this beautiful girl, and luckily for him, Naho also fell in love with him. Naho was sweet, affectionate, and always comforted him with his insecurities. But Yamaguchi knew that Naho had an ex, Oikawa, who was more attractive and better at volleyball than Yamaguchi. Clearly, Yamaguchi became obsessed with the idea that Naho was still in love with Oikawa, but Naho clarified many times that this wasn't the case. Even so, Yamaguchi felt so bad and became trapped in his own insecurity that he broke up with Naho.
After that breakup, he still loved Naho, but in that vulnerable moment, a girl appeared, Arely, a very pretty girl who became Yamaguchi's best friend as they had many things in common. Arely was in love with Yamaguchi, but Yamaguchi didn't forget Naho.

• That way you'll look more handsome
  Arely said, laughing, as she braided Tadashi's hair with flowers, while Tadashi watched Naho chatting with her friends in the distance.

Yamaguchi still loves Naho, even though Arely is with him. He loves Naho with all his heart and wants to get back together with her; that's his goal—to be with Naho.