These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Ho Yay: There's a whole lot of homoeroticism between the members of Dragon Sound. They're five guys who live together, go shirtless through most of the film, and sing about what good friends they are. In one scene, Jim walks around with his pants unzipped and shirt off, proclaiming that he's going to use the shower. In another scene, Mark goes around feeding grapes to the other guys.
The band's trip to the beach serves no particular function, and the establishing sequence goes on twice as long as you'd expect.
The biker party serves no other plot function than to establish that Hashito is aware of Dragon Sound's existence. Otherwise, it appears as though the filmmakers were simply impressed by the antics of the bikers and decided to add them to the film.
So Bad, It's Good / Narm Charm: It is somewhat controversial as to which of these two tropes fits the film better. Both are likely responsible for its new cult following in the 21st century.
Vindicated by History: The movie was harshly received when it was first released and was only in regional theaters for two weeks. Now, it has become a cult classic, with one critic saying that it has a nice and goofy charm to it, even though it makes The Room look like an Ingmar Bergman film.
The Woobie: Poor Jim. His mother died when he was young and his father was missing for most of his life. It's quite heartwarming to see that he has finally found his father but later takes a dark turn when he gets injured by ninjas along the way. Thankfully, he gets better and meets his father in the hospital.