Haikyuu is a work with a multitude of unique themes. However, if I had to choose only a few words to summarize the theme of Haikyuu as a cohesive whole, it would be “growth through connections with others.”

This idea is explained as early as chapter one, immediately after his loss, Hinata realizes, “I can’t do it alone” and begins to work with other players who he rejected before.
I don’t need to elaborate much on this theme in regards to Hinata and Kageyama as it is evident.

The literal driving force of Haikyuu is the relationship of Kageyama and Hinata, and how their partnership and rivalry allows them to new heights they could’ve never reached alone. They constantly challenge each other to never stop growing and moving forward.

Takeda makes this theme explicit in ch 15, “Nothing will happen if you remain separate, when one person encounters another, it causes a chemical reaction.” Hinata and Kageyama are the epitome, but it’s certainly not exclusive to them.

Smaller reactions are the prime factor in any major development in the series. Characters force each other to challenge their beliefs and see things in a new way, friends, enemies, and teammates alike.

To me, the primary plot of Haikyuu is Hinata and Kageyama and the secondary is the Nekoma and Karasuno rivalry. In present, this is shown as an epic match, a clash of the ages with intertwined stories. But let’s go back a bit. To two boys playing volleyball against one another.

A chance connection between Ukai and Nekomata. A reaction that the impacts of can’t be overstated. It leads to a rivalry that spans for generations, that fundamentally changes many people involved in it. This one reaction led to more than anyone could’ve anticipated.

The extent of these branching connections is impossible to measure. A great one to point out here specifically as caused by the Neko/Ukai rivalry is Tsukishima. His growth was spurred on largely due to the influence of Bokuto and Kuroo. (as well as Yamaguchi.)

The Nekoma motto of “connect” is very fitting. Honestly, I could go on forever listing examples. It’s almost, if not actually, impossible to think of a character in the series whose growth was not shown to be largely spurred on by someone else.

To list a few of the top moments: Iwaizumi telling Oikawa “six is stronger”, Hoshiumi telling Hirugami to quit, the influence of Kiyoko/Hinata on Yachi, Ushijima’s influence on Sakusa, Noya inspiring Asashi, Kinoshita’s hero moment, etc etc etc.

I’d like to point of two of the people Hinata’s had the largest effect on. Kenma and Washijo. With Kenma, Hinata was influenced along the way as well, but a significant factor of the foundation of their relationship was Hinata’s promise to him, “I’m make you say it was fun!”.

Hinata challenged Washijo’s notion of strength. Washijo allowed Hinata the ball boy opportunity which was fundamental to Hinata’s growth. And ultimately, Hinata freed him of the grudge of those 40 long years and helped him remember what it felt like to fly.

These two connections were already significant, but what makes them really stand out is that both Kenma and Washijo ultimately directly enable Hinata to go to Brazil. Without those connections, it may have been simply an impossible dream.

I think this demonstrates the sheer significance of these interactions. These reactions had a clear tangible effect on Hinata’s opportunities. As he knew from chapter one, he can’t do it alone. The connections he built over his years all culminated in him being where he is today.

And not just him, but every character is shown to be able to reach where they are today as a result of those who helped them and challenged them along the way. They are lucky to meet each other, lucky to play volleyball with each other. because, if we’re not alone, then...

I also recommend checking out sar’s thread about the importance of growth as a theme, it’s basically the other half of this, the connections help lead to this important growth we get to see in the story https://twitter.com/kitakitsunes/status/1279287727893053445?s=21 https://twitter.com/kitakitsunes/status/1279287727893053445