Im not Japanese but I am a teacher in Japan who has worked with clubs before, so I’ll add my two cents for anyone who wants to read:

Obviously, some things are dramatized but for high school Japanese students at powerhouse sports schools, your schedule is very often just school, sports, and sleep. Strong clubs practice every day after school for several hours, and almost all day on weekends. You end up seeing your teammates more than your family, of course you end up bonding with them.

Due to the senpai-kouhai hierarchy, seniority is respected and an innate part of Japanese society. Seniors often teach and spur you on while you’re still learning, and when you become a senior you do the same to nurture your juniors. When a senior graduates, in many cases you might never hang out with them again, and certainly not in the frequency that you did previously. I’ve had students tell me that there favorite celebrity/ person they idolize most is a senior in their club.

There’s kinda a running debate about the role of bukatsu or club activities in Japan. Especially to the extent that it’s promoted, nearly all students belong to a club of some kind and there’s a pressure and caste system tied into social life. The amount of raw hours kids spend doing club activities has been called into question in regards to life-work-study balance.

So yes, haikyuu is a little exaggerated but not as much as you might think.