- Pippi Osu is well-liked by the fandom. Maybe it's because she's a gamer. It helps that she's an authorized cameo of osu!'s mascot.
- Midori Gurin was expressly created as an Audience Surrogate Hate Sink whose main traits are that she's dumb, annoying, and constantly asks stupid questions. She's one of the most popular characters in the game and has essentially become YanSim's second mascot.
- Budo Masuta, the Martial Arts Club leader introduced in the mid-November 2015 build, is easily the most popular of the male characters. This is largely to do with him being a badass who can easily curb-stomp Yan-chan if she doesn't level up her strength or the player isn't skilled at the minigame. It also helps that he has more characterization than most other male students. More than a few players have declared that Yan-chan should stalk him instead.
- A lot of players love Oka Ruto, also introduced in the mid-November 2015 build, despite her explicit designation as a Rival (though in the debug builds she is only a club-leader NPC). This is because they find her unique mannerisms and personality endearing, and find her shy I Just Want to Have Friends personality with heavy Broken Bird implications to be very sympathetic. As an illustration of this, a Reddit post shortly after the rival introduction video came out asked how players would eliminate each rival; nearly everyone said they would spare Oka's life.
- While the character has been in the game from almost the beginning , the "Personality Types" updatenote gave Yui Rio a huge boost in popularity due to her being used to test the "Evil" persona. She is currently the only student with that particular persona. Needless to say, a member of the Rainbow Six turning out to be evil (even for testing) was an interesting surprise to some. Naturally, some fan-artists (as well as those YanDev commissions) have run with this.
- Sadly, Yui Rio has been removed from the game as of late. It's not known if she'll be returned.
- Placeholder-chan a literal Blank Slate non-character only in the game to provide club functionality had fanart of her mere hours after the update video of her was uploaded. Mom0ki (the voice of Midori, Oka, Kokona, and Saki) has even said that the soulless husk is her favorite character that she doesn't voice.
- This all probably led to the Empty Demon's implementation into the game.
- FUN GIRL already has a lot of attention from the fans by virtue of being a programming Easter Egg, a Nightmare Fuel Station Attendant, and a Shout-Out to W.D. Gaster.
- Flame Demon is probably the most popular out of three demons found in Demon Realm, thanks to his voice, role in Burning Love, and being similar to Grillby in design.
- Mr. Jazzy Feet, the Light Music Club's pet turtle, has lots of fans due to being probably the most adorable thing in the entire game, as well as his status as a Memetic Badass.
- The gender-flipped Bishōnen rivals from the April Fools' Day 2017 introduction video have attracted quite a lot of attention. Many fans are on board saying they would be happy to have them in the final game, even expressing interest in the idea of a potential Dating Sim with Yan-chan as the object of their affection.
- The Yakuza. His dark, dangerous presence and compelling character, even though he's only appeared in development videos so far, has attracted lots of attention. The fact that he's oddly sympathetic and quite pretty probably helps.
- Yandere-kun, the gender-flipped version of Ayano, is very popular with the fanbase, despite not being in the game unless one cheats.
- Out of the new Student Council members introduced, Shiromi Torayoshi seems to be the most popular.
- She's not implemented in the game yet, so her exact role is undefined, but the Delinquent History update made a lot of fans really like Genka, the guidance counselor, for her endearing personality and willingness to put her job on the line to help five students she failed to help when they were horribly bullied.
- The members of the Photography Club, all Expies of Mystery Incorporated, got a lot of love very quickly once the club's members other than Fureddo were implemented.
- Miyuji Shan and her Light Music Club became instantly popular for their fun personality and colorful Punk Girl design. They're also kind enough to let Ayano join their band, which can skyrocket her popularity if she plays well.
Ensemble Darkhorse / Yandere Simulator