A character's personality, worldviews, hobbies, and more can be clearly revealed in any work of fiction by personal details such as their clothing taste, word choice, and, of course, their living space. This is especially true in Japanese animation, where the characters are bright and expressive. However, for some reason, the character's own living space, such as their bedroom, is rarely included.
Many anime series set in the real world, such as slice-of-life series, will depict the main characters in their personal environment, such as an apartment or a suburban Japanese home. This is a missed opportunity for additional character development, and many anime characters share the same generic, uninteresting bedroom. However, a few other characters' bedrooms actually say something about them, which sets a good example for other anime to follow.
Interchangeable Bedrooms for Anime Characters
Experienced anime fans have no doubt seen the same generic bedroom design many times, serving as a basic backdrop for rom-com or slice-of-life antics. Such bedrooms usually feature the same few elements: a bare wooden floor, a generic, uncluttered desk, one or two bookshelves with hardback volumes or a manga collection, a simple bed and perhaps a school uniform or work outfit hanging on the wall. This makes for a reasonably comfortable and pleasant-looking living space, but it's also a disappointment to learn nothing about a character from their bedroom, a place where they can truly be themselves.
A variety of anime protagonists are generic and highly relatable people on purpose, being self-inserts with equally basic bedrooms to match. In a few series like Kubo Won't Let Me Be Invisible or Komi Can't Communicate, that may be the point, and in such cases, it works well. Sometimes, a bedroom really is just a bedroom -- a functional part of the character's residence where they'd entertain guests from school. Otherwise, though, these interchangeable bedrooms look like something from an interior decor catalog, and they may feel eerily similar from anime to the next. It's almost like these characters are all sharing the same house, rotating in and out as anime seasons start and end.
From a production standpoint, perhaps creating these generic bedrooms is a way to save money while not overburdening the animators. They don't have to draw or paint clutter like clothes all over the place or a few sports items in the closet, and manga artists may feel the same way. These simple bedrooms can also be used as a blank template to make the main character more relatable as a self-insert, having a simple bedroom that anyone could have. Then the audience can decorate that room with their own personal tastes in their head, such as wondering if Shoko Komi might add some potted flowers to her room or if Junta Shiraishi in Kubo might add a bean bag chair or a dartboard and cool music posters.
When an Anime Character's Bedroom Speaks Volumes
Other anime characters, usually protagonists with strong personalities, will have a bedroom that reveals something about them, whether or not it is surprising. The on-campus dormitory found in My Hero Academia, where classes 1-A and 1-B settle into a large dorm for their own safety, is a prime example. Each student can furnish and decorate his or her own room, and the anime spends a few minutes amusingly exploring most of class 1-A's private chambers.
Most of all, the anime focused on protagonist Izuku Midoriya's room, which looks like an All Might museum, much to poor Deku's embarrassment when his classmates see it. Momo Yaoyorozu, who's used to living in her family's wealthy bubble, accidentally fills her entire room with a single giant bed, suggesting that she still has much to learn about looking after herself and navigating the world outside of her family's estate. Ochaco Uraraka decorates her room more subtly, having generic furniture and decorations except for one thing: the star chart on her wall. Official My Hero Academia lore fluff says that Ochaco loves watching the starry sky, so that star chart in her bedroom is a clever little addition that only the savviest fans will pick up on.
Naruto also has a thematic bedroom, though it's only briefly seen in early episodes. Protagonist Naruto Uzumaki lived alone, with the Third Hokage only peripherally supporting him, so Naruto was alone in an apartment that he always kept rather messy. Naruto was fairly self-sufficient for his age, but he was still a 12-year-old boy, so naturally, his room was messy and cluttered, and he even had a carton of expired milk in the fridge. It was amusing, informative and vaguely tragic to watch an unpopular, misunderstood tween boy get himself ready for the day in his apartment, only barely keeping his life together like that.