r0xm2n

Hani Rei https://vndb.org/s131 (Matsushima Michiru from Grisaia). Michiru's voice is so friggin' adorable. She has the goofiest, and girliest laughs ever. Also funny when Michiru flips out for whatever reason.
Runner up is Simizu Ai https://vndb.org/s416 (Komine Sachi from Grisaia). Sachi has a rather quite voice ..... but MAN, can she moan in her erotic scenes!

^^^
ChiruChiru best VN girl ever. Have fun with her route....

Grisaia has a few sidestories (The Leisure of Grisaia, and the Idol Magical Girl series). Nice if you want more Grisaia, or just more ChiruChiru (she's my most favourite character ever)
I've only played a small handful of VN's, so I can only recommend Kono Oozora ni Tsubasa wo Hirogete (If My Heart Had Wings) https://vndb.org/v9093, and Wagamama High Spec https://vndb.org/v17823. Both games are more light hearted then Grisaia in general.
If My Heart Had Wings is pretty good. Some of the flying scenes are breathtaking, and the music is good. The plot is pretty good despite it being light hearted. The eroge scenes were pretty good too.
Wagamama High Spec is even more light hearted. It's a parody on eroge and manga in general. And the eroge scenes are pretty high quality (this is the game to get if you really want some fap material). In fact, there's almost too much eroge here...
 
I guess I'll post some of my VN wishlist too (VN's I'm considering playing in the future):
* Steins Gate (probably the gold standard when it comes to gripping and engaging plots).
* CLANNAD. I've heard nothing but great things about this.
* Doki Doki Literature Club! (don't let this seemingly happy looking game fool you....).
* Himawari https://vndb.org/v210. Apparently the remake is recommended (even though it doesn't have the +18 content). And apparently it's feels will hit you like a truck.
* G-Senjou no Maou https://vndb.org/v211. I seriously can't wait for this crime thriller (I'm waiting on the unrated version with bated breath).
* Subarashiki Hibi ~Furenzoku Sonzai~. +18 patch unlocks 90% of the story too. Apparently this VN is pretty disturbing....
* D.S. -Dal Segno. https://vndb.org/v17742 Looks like a typical eroge romcom.
* Koisuru Natsu no Last Resort https://vndb.org/v13046. Another eroge romcom.
* Nekopara series. If you want cat girls, and lewd action xD

Recommendations in Bold ~
I gather, that you liked the emotion/heart-wrenching aspect of grisaia.
Try,
Key VN's -> Clannad, Little Busters, Rewrite (no-h, but you are probably better of here)
Narcissu  (no-h)
Majikoi -> Slice of life/School life is very good, Routes such as Wanko's can be very emotional (enough h-content to make up for the above games)
Minori games -> ef, eden* Route structure is very different than what you are used to but it will hit you in the feels . (there is h-content)
Enigma -> unvoiced, but really very good, very emotional (no-h)
Yume Miru Kusuri -> This also deals with girls and their problems, (bullying, drug abuse) (there is h-content)

Never even heard of this VN before. But color me very interested.
I'm kinda a fan of the conceited super genius loli types

Sachi's, and especially, Michiru's routes are emotional rollercoasters (compared to the other routes). I teared up in both routes actually. Amane's has an amazing flashback though (that left one heck of an impression).
As for Yuuji's decisions in Maki's route, well the Grand route in Labyrinth of Grisaia sheds some light on that...

And yeah, Michiru is the best girl.

If you want to discuss VN's, you came to the right place. Welcome!

Nice to see someone else reading Grisaia. That was my first VN ever actually, and it's something I'll never forget.
Enjoy your stay on these cool forums.

Grisaia no Kajitsu https://vndb.org/v5154 and Kono Oozora ni Tsubasa wo Hirogete https://vndb.org/v9093 would fit the bill. Both are high school slice of life affairs with romance and comedy. Both are censored for western releases, but both have patches to restore the censored content (Grisaia unrated version can be bought directly from Denpasoft too). Both have +18 content.
Kono Oozora is the more light hearted of the two, and it doesn't even have any bad endings (the sudden cutoff ending where you fail to flag a route doesn't count). Some of it's scenes and music are breathtaking (it is a game about flying afterall).
Grisaia is very well written, has endearing characters, and has somewhat over the top comedy ..... at first. Things get rather serious when diving into the backstories of the heroines. The good endings are good though.
 
I don't have any other suggestions, as those games (and Katawa Shoujo) are the only VN's I've played so far.

Someone already mentioned An-chan (Tatsuya) in If My Heart Had Wings. He's definitely an older bro to the protagonist. Game also had Ma-bou, but he's just there for occasional comic relief...
Grisaia No Meiyuu also had Daniel Bone (yes, that is his name), and a few other supporting male characters. But that game is the 2nd part of a trilogy....
Katawa Shoujo had a teacher, and the nurse, that were supportive (depending on the route).