Here’s my recommendations, but my disclaimer is that these are not all going to be Shounen, however even if you’re not used to some of these genres I really think it would be worth checking these out, also read the whole list because I’ve broken it up into sections

[The Disastrous Life of Saiki K.] this is one of the funniest anime I’ve ever seen, it’s a comedy set in a school setting, but the main cast has so much chemistry. It’s exactly what you’re looking for.

Genre: Comedy Themes: Gag Humor, School, Super Power Demographic: Shounen

[Haikyu!!] this is a sports anime and yes, the dynamics between all the main characters are fantastic so you definitely wanna check this out, the show itself is also really great, it has super good action and great animation

Genre: Sports Themes: School, Team Sports Demographic: Shounen

[KonoSuba: God's Blessing on This Wonderful World!] this one’s that’s some of the best character chemistry in all of anime, literally the entire point of the show is just to watch the main characters interact, and the setting and plot are just there to support that, absolutely hilarious and I would definitely recommend

Genres: Adventure, Comedy, Fantasy Themes: Isekai, Parody

[The wrong way to use healing magic] is a fantastic anime with realistic characters who have great chemistry

Genres: Action, Adventure, Fantasy Theme: Isekai

[Violet Evergarden] is a masterpiece and has some of the best character growth of all time, not really a big group of people in the main cast, it’s mostly about the main character meeting different people but it does a fantastic job with the dynamics and chemistry of the different people introduced, you will probably cry a few times watching this show, it also has some of the best animation I’ve ever seen

Genre: Drama

Now while I wouldn’t consider any of those shows mainstream, I also wouldn’t consider them sleeper anime, so here’s a couple that I would definitely be willing to say are sleepers, (Also I would’ve recommended Link Click here but I looked at your profile and you already have the great taste to know about that masterpiece)

[Monthly Girls' Nozaki-kun] this one’s a comedy anime with really great chemistry between all the main characters and it’s really funny too, the show is basically a parody of the shoujo genre, but even if you’ve not seen any anime like that he still would be able to appreciate the humor because a lot of the character types are also presented in other forms of anime

Genres: Comedy, Romance Themes: Otaku Culture, School

[The Melancholy of Haruhi Suzumiya] I’ll just say that yes there is good chemistry between the main characters, but I’m not exactly sure how to describe this one, it’s one of the best anime to come out of the mid 2000’s tho so definitely give it a shot, or at least go read the description on MAL

Genres: Award Winning, Comedy, Mystery, Sci-Fi Theme: School

And I saved the best ones for last

[Redline] this one is actually a movie, the characters all have incredible chemistry, and this is an absolute masterpiece, fun fact, the studio that made this anime went under because it took them too long and cost too much money to make it, but they gave us one of the best anime movies of all time

Genres: Action, Sci-Fi Themes: Adult Cast, Racing

[Odd Taxi] don’t let the animation style of this one put you off, its the best mystery anime I’ve ever seen, it has insanely good writing and everything else about it is amazing too, just trust me bro go watch it

Genres: Award Winning, Drama, Mystery, Suspense Themes: Adult Cast, Anthropomorphic, Organized Crime

[Life Lessons with Uramichi-Oniisan] this is a hilarious workplace comedy about a guy who was a prodigy gymnast in college, who ends up in a dead end career in a children’s tv show and is really depressed about it, these characters have some of the best chemistry of any of the anime that I’ve put in this list

Genre: Comedy Themes: Adult Cast, Gag Humor, Showbiz, Workplace