Things to know about the nature of this story...
Is HR a harem game? Yes, in the sense that the PC/male protag is romancing and getting with a gaggle of girls.
Is this a 'classic' protag only centered harem a la the girls only give a shit about the MC and that's it, like say... Highschool DxD? No. This is a harem of the polyamorous 'everyone goes out with everyone within the harem or sub-harems' like a more extreme version of Nekopara. And, since most of the cast are women, that means that there will be a fair bit of yuri bc... the MC is not the only person who matters in the relationship even if he/we are the center of it. Again, 'everyone is going out with everyone'. Better get used to that... or leave.
Why does this distinction matter? Because one, this is a strictly 'group focused' harem and two, there are multiple, interconnected sub-harems that can can be roughly divided like this, starting with the Main 21 and their supporting cast:
- Main Girls: Your 9 housemates. They have links and connections to other characters/groups to varying degrees of closeness. Chitose's coworkers are less side sub-harem that attached to her but are just that, side girls while Kanae, Sakura's mom, is a supporting sub-heroine for her story, and Ai has her senpai Honoka and her 'daughter' who you name and is currently a cute robot toy atm....
- Main Sub-Harem 1: Honjo Group, which is further divided between Fumiko, Satsuki, and Tsubaki and the 'Three Idiots' of Hizumi, Tsuyomi, and Setsuna... though, these 3 are more supporting harem to the sub-harem here. Otome, of the 'Main 9', is the common link here due her knowing Tsubaki and being friends with her.
- Main Sub-harem 2: Aoi's group of herself, Mako and Nagi. Aoi is connected to Fumiko, but Mako and Nagi are the MC's kouhai/juniors from his high school days and has Mizuho, Mako's mom, as her supporting sub-heroine.
- Main Supporting LIs 1: These girls are directly related to one of the Main 9 but aren't part of a harem themselves.. Meiya: Maya and Miya's mom and Sanae, Ayase's half sister. (These roles only apply if you're running the uncensored 'aletheia run' though. I don't know, or care, what their roles are otherwise but doesn't really change their status as heroines or supporting role nature to the Main 9). Meiya has Erika and any other Suzuki Group girls as support characters but who are also not yet sub-heroines themselves... yet.
- Main Supporting LIs 2: These include the girls who both don't belong to a harem of their own and/or are only really relevant to the MC himself and have next to no interaction with the other girls or groups. These include the 2 Level Up Ladies of Nagisa for the gym and Megumi for the library, and the two store girls of Yuri and Kaori. You can think of them as the side girls with ongoing stories who are far removed from the rest of the cast and are pretty much MC exclusive.
- Side Sub-harem 1: The Platinum Cafe girls.
- Other Side girls: Aurora massage parlor clients like Sayo and Suzume the pool attendant.
More WILL be added later as the story demands.
Now, aside from the side girls, the main 21 and their related cast are unavoidable capture/romance targets and aren't skippable as far as the actual story goes. Turn back if you're not a greedy bastard who wants ALL the heroines.... you've been warned.