4 girls total, with a 5th one recently introduced as far as I've read though I'm not fully caught up yet (84/95, skimmed 87). You've got the four season girls mainly. Haru(Spring), Fuyu(Winter), Aki(Fall), and Natsu(Summer). The author has expressed interest in adding more girls and has introduced Tsuyu (rainy season) Saki explicitly as a fifth girl as of 87 (based on author notes). Souhei knows he's basically raping the girls and doesn't really regret it since he's horny and wants to explore the dungeon because it's in his blood, but also tries to make sure they're happy. Which, surprisingly, they actually really are and not entirely because of mind control.
- Harumachi Hashira, the maiden-like teacher.
- Very athletic body, best proportions. Has sex with Souhei early on because of the candle and thinks she raped him. Goes to apologize later, but gets called by the dungeon and finds out about it, though not the items since Souhei lies. She bans him from entering for his safety so Souhei uses a bell to give her dreams of him molesting her and makes her think that he'd be suicidal if he isn't allowed to enter the dungeon. She ends up going with him into the dungeon since she thinks she has a crush on him and doesn't want him to be sad. She's actually a very well trained staff fighter (it's her family martial art and she was basically raised as the male heir) and she's very good in battle. Is also shot once by a crossbow that increases her love for him. Souhei uses a drug thing on her that makes her really want to suck him off, making her think she has some sort of uncontrollable problem that makes her want to randomly sexually assault him. Fuyushima tells her about the items later (following a somewhat heroic moment from Souhei in the dungeon) after judging that it would be fine to do so, and she was right as Harumachi didn't care at that point. Is extremely bad at being feminine to the point she took her own virginity in the past because she thought it would make her more womanly (it obviously didn't). Puts on a dress for the first time ever to look good for Souhei. Probably the most innocent and naive of the girls despite being the oldest.
- Gets a Wind God item that allows her attacks to miss anything except for enemies in the dungeon, which apparently includes air resistance letting her do stupidly powerful attacks and techniques. In exchange she'll really want to have cosplay sex.
- Fuyushima Enishi, the emotionless doll.
- Very slender, second smallest breasts. Literally has no emotions. Was told by her parents to hide that fact because they knew she'd be easy to take advantage of otherwise. They also told her that she'd one day meet her "Fated Person" who would awaken emotions in her and that she should only have sex with that person. Souhei uses a drug on her to make her suck him off, which she does without caring because no emotions. He uses a ticket on her that lets him sleep over with her without anyone thinking it's strange, and he uses a bracelet thing that lets him grope her without her noticing. She gets turned on and has sex with him, asking if he's her Fated Person. She later thinks he really is her Fated Person after seeing her turned on face in the mirror. Follows Souhei's commands and sexually trains herself according to his wishes. Is called by the dungeon after the dungeon lures Harumachi to the rooftop to distract Souhei, at which point Fuyushima finds out about the items (gets the same journal thing Souhei does) but she doesn't care since she has no emotions. She's actually very interested since she thinks one of the dungeon items might be able to give her emotions and her parents told her that having emotions was a good thing. Bargains with Souhei to get him to use the umbrella on her (~11 minutes total under umbrella) and feels love for him (arguably really making him her fated person) and Souhei thinks that she may start to feel other emotions since she actually likes something now and thus disliking something would naturally follow. Is slightly yandere since love is the first emotion she's ever felt and the only emotion she's feeling thus far. At one point started ending all her sentences by telling Souhei she loved him. Very loyal to Souhei.
- Gets a Water God Anklet that lets her great a barrier with various effects and a duration dependent on the amount of times she's had sex. It also makes the wearer feel and believe they're definitely being impregnated if they wear it during sex (the other girls are jealous).
- Akitsu Maya, the high specced intellect.
- The curviest of the girls. She puts on an airheaded facade most of the time, but is actually incredibly curious about things and is the sort of genius that's generally bored with life. Realizes quickly that something is up with Souhei and his attempted use of the umbrella on Natsuno (wants to set her up with him at first to try to make her happy), but not that the umbrella is the problem or what happened. Her interest in him manifests in a lot of curiosity about him that gets compounded when the umbrella is used on her. She tries to find out what he did to Natsuno and herself a lot and tends to let her real face show when investigating him. She's willing to have sex with him in exchange for the knowledge, but won't sacrifice Natsuno to him for it. Tries to trap him with a video camera while he used a bracelet that prevented her from noticing him groping her, but the bracelet prevented her from noticing even through recording and in her dazed and horny state ends up believing him when he lies that he randomly produces pheromones that attract women (she's ecstatic that she creamed herself just by being in his presence since it's new and exciting to her). Interrupts him a few too many times while investigating him and protecting Natsuno so Souhei uses a ticket to sleep over with her, takes her to a love hotel, uses an hourglass to freeze her conscious for 30 minutes, then uses the umbrella on her for the entire time (~40 minutes total under umbrella). She comes out begging to fuck him and he goes at her pretty hard as punishment for getting in his way so much. She ends up being very useful since she's very smart and helps him manage his little harem and public perception in various ways. Is very proactive about being a "useful sex friend." Sets up a private chat group for his harem where one of the rules of the group involved sending selfies (mostly nudes) to him every morning and organizes schedules for the harem and everything. Finds out about the items after getting called by the dungeon along with Natsuno and picking up the journal thing that Souhei got, but doesn't care beyond being curious about the dungeon. Tends to be plotting a lot in the background, but entirely for Souhei's sake after he takes her. Extremely interested in how the dungeon functions.
- Gets Earth God Misanga that lets her produce breast milk (Melk) that heals in the dungeon. She feels pleasure when people suck her Melk.
- Natsuno Hiyori, the masochistic prez.
- Extremely childlike body. Is strict and sharp tongued to most people, but because of the umbrella she's rather a blushing mess in front of Souhei and acts more like a puppy for most of the story. Gets the bell used on her so she dreams of Souhei molesting her and whatnot and ends up too embarrassed to even leave her room afterwards (basically faints in her room when he rings her doorbell and says hi on voice comm). Actually has a really bad home life since her parents are divorced in all but name and they don't even live in the house with her. Is very lonely and half the reason Akitsu acts the way she does is for her sake. Souhei uses a magazine that'll make the reader see their sexual desires and finds out that Natsuno actually really wants to get raped. He uses a ticket to sleep over with her and proceeds to sort of not really rape her. He makes her breakfast in bed afterwards. Natsuno finds out about the items alongside Akitsu after getting called by the dungeon and is sad, but on Akitsu's suggestion she willingly stays under the umbrella with Souhei until she loves him enough that she doesn't care anymore (~26 minutes total under umbrella). Ends up moving in with Souhei when he finds out about her home life and basically acts like a submissive little newlywed wife with him. Is incredibly masochistic to the point she's excited at the thought of being treated poorly and Akitsu directly tells Souhei that Natsuno would be happier if he didn't treat her well. Sucks at hiding how happy she is at the thought of being abused, but also likes romantic gestures.
- Gets a Fire God Choker that lets her imbue fire into her attacks. It also makes her want to have sex outdoors the more she uses it (she's extremely eager to use it when she reads the description).
There's a Tsuyu Saki (half-Japanese ballet dancer in a rundown amusement park) that's introduced in chapter 87, but I've not read that far yet beyond skimming a bit. It's telling what kind of person Souhei is though that his first thought is to use the bell on her and only doesn't because he's on a date with the four girls and doesn't want to ruin it (rape-y as heck but prioritizes his harem's happiness over his desires). There's also the will of the dungeon that's described as childish and is maybe female. It has possessed the girls in various ways to interact and talk to Souhei, but is mostly a mystery thus far.
As a side note, I don't actually find the writing in the WN all that great and the sex isn't all that stimulating. The sex scenes are only interesting for the situation aspect of it since the actual sex itself feels like it's going through the motions more than not and is somewhat repetitive. Even the 5P scene was just boring and I ended up skimming most of that. The manga will definitely be more interesting in that regard since the decent art provides what the writing really doesn't.