Leave it up to handsome coach Akira to make sure that the Aota Academy's girls volleyball team members learn excellent technique and ball control. In the first episode, volleyball ace Nanase joins the team, but she can only get fired up to play when the coach gets her "hot." When Akira gets beaten up and sent to the hospital, how will the team be able to compete in the championship if Nanase can't get in the mood to play? Find out in this fun and funny sexy adventure!

Why is anime so popular in Japan?

It's pervasive but I wouldn't call it "popular".
Here's how it works Anime (but mostly the written form, "Manga") is everywhere and not just in the form of comic books.
It's used to explain how to sort your garbage, it's used to tell you not to harass people in trains, it's used to make a product more cute (kawaii).
WHY? I could argue that the Japanese are masters of design and have learned that images convey meaning faster than text. I could take an art-historical perspective and say that it goes back to ukyo-e wood block prints that became popular in the 16th century.
I could go logical and say people spend a LOT of times on trains and comics are an easy form of entertainment I could go anthropological and say that it's because japanese think it's always been that way and are pretty in to the whole "I do this because everyone does this" mentality. That being said, let's talk about "popular".
It's not, and you're not if you're really into it. I think this is the biggest shock for foreigners who go to Japan.
Anime is not cool.
Being an "otaku" is not cool, not even in the ironic sense.
Most people I knew in the US who were in to anime weren't exactly the popular kids (myself included) and assumed that going to japan everything would change.
Like, magically, you'd be in this world where everyone had the same interests and you'd have all these people to talk to who totally get you and think you're cool.
Works. The reality is that being into anime in Japan is just as frowned upon as being into anime anywhere else.
The major difference is that it IS everywhere so, if you want to get lost in anime, you totally can and a lot of people do (so maybe this is the popular part?) but, doing so is not something to aspire to, and not something that's well viewed by the majority of native Japanese, or foreign ex-pats.