Despite the surprising popularity of the source material outside Japan, the game had very little online presence, though the manga's author Okayado has drawn fanart of some of the characters.
The player took the role of a host family for the Interspecies Cultural Exchange Program, looking after a number of non-human guests, all of whom are female, as they learn to integrate into human society and possibly find love.
Gameplay was based around acquiring various character cards, all with different stats and abilities, through a gacha system and taking them on outings into town. During these outings, your party had to fight off hooligans and delinquents. Combat was mostly automated, though the player could cheer for their characters up to three times per battle, which can guarantee a Critical Hit or halve incoming damage.
While the game shared many elements with the manga, there are some differences, mainly caused by the lack of a dedicated main character and a slew of new characters.
Sadly, it had lasted for less than a year, and shut down on November 22, 2016.
Daily Life with Monster Girl Online provides examples of:
- All Myths Are True: In keeping with the manga, though the game expands it by having even more, often obscure, monsters.
- Anti Poop-Socking: Taking a girl out on an outing drains some of her stamina, and if her stamina gets too low, she can't go out anymore and you'll have to either switch her out for a new character or wait for her to rest.
- Bribing Your Way to Victory: The game's premium currency, rubies, can be used to play the high rarity gacha, fully refill a girl's stamina, and purchase temporary stat boosts that greatly increase the strength of all characters in a given type. While rubies can be acquired without spending a cent, they're more readily obtained by paying real money.
- In addition to the standard ruby gacha, there's also a Once-Per-Day DMM point gacha that has a greatly improved chance for SR characters, and is guaranteed to give you the most recent HR girl.
- Com Mons: Any of the N rarity girls, who drop in abundance from every map in the game.
- Disc-One Nuke: Miia is the first character you ever get, and has stats that allow her to remain useful all the way up to 6 star difficulties, though she is outclassed by other SR characters and even HR characters acquired from the gacha.
- A Dog Named "Dog": In keeping with Okayado's awful naming sense, most of the characters are named after their species.
- Elemental Rock-Paper-Scissors: Each girl has one of five personality types, Passionate, Cool, Cute, Pure and Devilish, which doubles as her elemental attribute when calculating damage during combat.
- Passionate types are strong against Cool types, but weak against Cute types.
- Cool types are strong against Cute types, but weak against Passionate types.
- Cute types are strong against Passionate types, but weak against Cool types.
- Pure and Devilish types have no advantages or disadvantages against the other three types, but deal increased damage to each other.
- Fanservice: The "Caregiving" mini-game to raise a girl's affection for you, which ranges from simply giving them a massage to helping them with a difficult aspect of their non-human physiology. Usually, this puts you into a rather risque situation and their reactions are very suggestive.
- Featureless Protagonist: The player character is a nondescript young man whose face is rarely seen, and when it is, it's mostly obscured or lacking in distinctive features. Although, he does share Kimihito's trademark Blank White Eyes.
- Infinity -1 Sword: Miia, Keros, Youko, Froze, Dina, and event reward girls have lower than average stats for their rarity in order to make up for how easy it is to get them.
- Miia is the first girl you'll ever get, and though she's strong enough to be useful even in the late game, she's massively outclassed by SR girls acquired from the gacha.
- Keros, Youko, Froze, and Dina can all be obtained from continued play, and one is given to you from your very first gacha. As a result, they're only slightly stronger than R rarity girls.
- Girls received from event maps require a bit more effort to get, but are slightly weaker than other HR girls since getting them just takes time rather than investing in the gacha.
- Infinity +1 Sword: Any SR girl received from the gacha. Their stats are so ridiculously high that they begin to outstrip max level HR girls before they even get half-way to their max level.
- Intimate Healing: Some girls' care events have you treating injuries that came about due to their unique biology.
- Level-Up at Intimacy 5: Raising a girl's affection via the care giving mini-game will greatly improve her stats.
- Marshmallow Hell: Fan Long inflicts this on the player during her care event.
- Moe Anthropomorphism: While some monster girls are based on actual humanoids, most are based on creatures that were decidedly not humanoid, such as the hydra, manticore, and cockatrice.
- Multiple Head Case: Rus the Orthros and Rubero the Cerberus have extra heads in the forms of puppet-like Super-Deformed canines in place of hands, each with their own distinct personality.
- No Plot? No Problem!: There's no real story beyond the premise of "Collect cute girls! Have them fight and level them up!"
- No Sex Allowed: Just like in the source material, interspecies fornication is against the law. There's nothing against fairly intimate massages though.
- One-Gender Race: In addition to the lamias, harpies, yuki-onna, and arachnes present in the manga, the game introduces others, such as jorogumo, banshees, hels, empusa, leann sidhe, honey bees, undines, and sylphs, among others.
- Our Monsters Are Different: They're pretty much all humanoid and pretty.
- Bee People: Literally, in the form of Queen and Honey. Queen is looking for a man suitable of becoming her king, and Honey came along to help her.
- Draconic Humanoid: Though just how humanoid can vary; some follow the standard Winged Humanoid with reptilian features style, while others are based on more serpentine dragons and bear a strong resemblance to lamia.
- Elemental Embodiment: So far there's Water and Wind in the form of Dina the Undine and Ariel the Sylph. Joined later on by Sara the Salamander(Fire) and Tiera the Gnome(Earth)
- Fauns and Satyrs: Shire is a very traditional satyr, possessing goat legs, horns, and being very...friendly. Additionally, we have Kehp the faun and Sophia the baphomet. Kehp is more sheepish, having a thick fleece and a timid nature. Sophia, on the other hand, has black feathered wings in addition to her goat horns and legs, and is a fan of black metal.
- Golem: One made according to the Jewish legend no less! Though she's much closer to a Ridiculously Human Robot in her mannerisms.
- Harping on About Harpies: In addition to Papi covering the "common" harpy, we have Kuune the Cockatrice, Bima the Garuda, Misaki the Yatagarasu, Haru the raptor, and Fi the Phoenix.
- Our Banshees Are Louder: They're closer to the classical portrayal, in that their cries merely herald a coming death rather than cause it. Nia in particular is a crybaby with a tendency to spot death flags in anime, and prefers stories with happy endings.
- Our Cryptids Are More Mysterious: And more patriotic, if Kalolo the Jackalope's stars-and-stripes bikini is anything to go by.
- Our Demons Are Different: In addition to Devils, who are Hades Shaded with a taste for old Japanese fashion, there are also Arabian Ghouls, red-skinned flesheaters that have to bathe regularly to prevent necrosis.
- Our Gargoyles Rock: They bear a strong resemblance to humans, save for their horns, bat-like wings, prehensile tails, and grey, stony extremities. Their skin also seems to be some kind of flexible stone-like material, as Chione's care event has you examining and treating a serious crack in her skin.
- Our Ogres Are Hungrier: Not to mention daintier and more fashionable.
- Our Orcs Are Different: They have Bizarre Sexual Dimorphism. Males resemble large, tusked boar men and have a keen sense of smell. Females are curvy, green skinned beauties with no porcine features save for their hooves and tails. Both sexes share a confrontational attitude and rotten personality though.
- Spider People: In addition to the standard arachne, we're also introduced to Kuruwa the Jorogumo, who resembles a human girl with purple skin, chitinous exoskeleton on her arms, spider legs extending from her back, and an arachnid abdomen attached to her spine.
- Unscaled Merfolk: Kyure the scylla and Kura the kraken both have tentacled, cephalopod lower halves.
- Youkai: There are few present, namely Kuruwa the jorogumo, Youko the kitsune, Tatake the bake-danuki, and Mai the kamaitaichi.
- Peninsula of Power Leveling: The daily outings, which always reward upgrade materials for a specific personality type depending on what day it is.
- Permanently Missable Content:
- Any girls featured as the reward for event maps. The only way to get them was to complete limited time maps, and there are currently no plans to bring them back or make them available again. At present, the list includes Miti the Yeti, Pirati the Vampire, Lyca the Werewolf, Actia the Mothman, Shitori the Lesser Devil, Rudy the Bastet, and Tiera the Gnome.
- Miti the Yeti was featured in a revival event about half a year after her first appearance.
- Play Every Day: In addition to daily requests that are an excellent source of upgrade materials, rubies and care cream, there are also daily log-in rewards.
- Power Equals Rarity: HR and SR girls obtained from the gacha, who have a 9% and 1% drop rate respectively, have stats far beyond your starting characters and those obtained just by completing outings.
- Power of Love: Cheering for your girls during combat will empower them, and doing so at the right time can be crucial to victory.
- Quest Giver: Myuu, the draconewt. In addition to giving you quests, she also rewards you for logging in every day, and helps mediate situations with rogue homestays.
- Single Woman Seeks Good Man: Several girls explicitly state this as their only reason for joining the interspecies exchange program.
- Yandere: Dina, the undine. She believes she's in a Reincarnation Romance story and you're the reincarnation of her lover. The problem is that she doesn't care that you don't agree with her, and is perfectly happy with using threat of violence to coerce you into acting the way she thinks you should act.
- You Require More Vespene Gas: You have three resources, Meat, Vegetables, and Bread, which are used to feed your girls after an outing and level them up. While they regenerate on their own, you'll have to send some of your girls on shopping trips to the grocery store in order to keep your pantry full.
