Ensemble Dark Horse / Yandere Simulator

• 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 until the rest of the students were implemented, he had more characterization than most other male students. More than a few players have declared that Ayano should stalk him instead.
• Kokona Haruka was just a generic student with a weird hairstyle, until she started being used as the guinea pig for new and more complex elemination methods, which made her the first student to have a fleshed-out personality and backstory. While YandereDev originally planned to let her fade into the background when her role was done, her immense popularity has led him to consider giving her bigger roles, such as giving the tutorial (as practice for a drama club play), being the victim of Kizana's task, or even being a post-story DLC rival. Or all of the above.
• 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^† (March 2015 to be precise), the "Personality Types" update^note (early February 2016) 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. Many rejoiced when she appeared as a student in 1980s mode.
• 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.
  • That said, in the Final game Mr. Jazzy Feet will just be an ordinary turtle.
• 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 has attracted lots of attention, especially when he was finally added to the game via 1980s mode. 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 four members of the Student Council, Shiromi Torayoshi seems to be the most popular.
• The Delinquent Backstory update made a lot of fans really like Genka Kunahito, the guidance counselor who has the role of punishing Ayano if she gets caught breaking school rules, 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.
• Nemesis-kun, despite only appearing in a Freeze-Frame Bonus near the end of the April Fools' Day 2017 introduction video, is very popular, commonly portrayed by fans as Ayano's Fetishized Abuser.
• Horuda Puresu, who was literally just a placeholder for a planned character, with YandereDev even saying people shouldn't get too attached to her. People fell in love with her quite quickly for her Creepy Cute appearance, hilarious skirt glitch and generally being one of the most pitiful characters in the game, being a frequent target for bullies, to the point where she's willing to murder the person she believes is responsible for her misfortune.
• Kokoro Momoiro is the most popular of the bullies due to The Reveal that she isn't so mean after all. After being bullied at her old school, Kokoro joined Musume's gang because she didn't want to be their target, which lead to her hating herself for what she became. She will go back to her old self if all the other bullies are killed by the player.
• Hazu Kashibuchi, the guy from the sewing room, is yet another shy cutie who is popular among fans.
• When it comes to 1980s Mode, the rival that draws the most attention is Ai Dourayashi, the idol singer from the sixth week. Fans liked her catchy song, her sweet personality, and were sympathetic to her canonical electruction fate. Her song was translated into multiple languages and one fan even created a Beat Saber level to it.