I've seen some comments and reviews posted that introduce the specific setting, characters, and story elements of this VN. This topic is going to be a more general/analytical writeup on the themes and overall presentation.
Now don't get me wrong. I'm not trying to downplay the dark/depressing elements. In fact, a handful of events may not be for the faint of heart, and the endings aren't always the happiest. However, mostly referring to these elements really downplays the true experience of BokuTen and may stop people interested from checking it out.
Bokuten actually has a good mix of legit emotional, heartfelt, heartwarming, and most of all, bittersweet moments. This might be an overused word to some people, but Bokuten is essentially a "Deconstruction" on the meaning of love and happiness. Moeges, charages, and even some storyge with romance tend to build towards some mostly happy ending where everything turns out alright.
Bokuten tends to ponder both the positives and negatives of a romantic relationship and what it's built on. Is truly getting together no matter what the best possible outcome for everyone? Who and what gets affected when you confess and/or get together? Can you really handle and love the other person unconditionally, flaws and all? All of these questions, and more, are potential themes to think about when you're reading through the story.
Similarly, it also raises the question of what the true meaning of happiness is and how to obtain it. This is a big theme for various characters.
In addition to these two important themes, Bokuten still has a lot of what it's in typical visual novels. It has comedy and lighthearted moments with some unique humor and some you see often (thank god there's no tsundere hitting humor). It has an MC that's oblivious to some romance, but obvious to everyone else. But the MC has a legit reason for feeling that way, and has much more personality (in a sarcastic/blunt sense) than others. If you've watched the Oregairu/SNAFU anime, think of him like Hachiman, but a darker take. Alternatively, think of him like Yuuji from Grisaia but instead of saying things to specifically troll and get on people's nerves, he is just that serious and to the point about what he thinks.
It also has a common route, but it's one of the most unique and interesting common routes I can think of in visual novels. While there are still slice of life comedy scenes as stated above, they aren't too long and each chapter gets to the meat of its drama pretty quickly. The common route is kind of a mix between Sharin/G-sen's chapter system and ef. The decisions you have to make can be difficult and the themes build heavily into what to expect in the actual heroine routes.
Speaking of choices, a big theme is the general grey area of what's the 'right' choice. Compared to most visual novel choices that are simply ways to get involved with heroines faster, every single Bokuten choice is a heavy hitting one that at least makes you think and there may not even be a clear right answer. Sometimes the characters struggle with these choices themselves without input from the player. Similar to real life, not every choice is just a simple way to get something. There may be sacrifice needed in order to achieve what you want.
In conclusion, while it is fair to call Bokuten a dark/depressing utsuge given how some endings play out, there's a lot more to it as stated above. If you're interested in finding a character oriented visual novel with more story than usual, but the utsuge comments deterred you, hopefully this post can help you reconsider. If you like utsuges and just wanted more motivation to read this, even better!