For those that like harem or simple but incredibly good vanilla stuff (with a touch of imouto), i recommend then:
-Summer Memories (plus its DLC Summer Memories+) and Winter Memories. These 2 games are prequel and sequel, starting from summer to winter. The quality of it is through the roof and animation is incredible. You can find them maybe here... in itch.io (not sure) or on Steam, but you'll need the +18 update that you can get from Kagura games official website for free, go through the game steam store page to get to the official website. Or if you want the Most pure version of it where there's no need for +18 patches ... but it will be in Japanese.. DLsite sells the game at discount price right now.
The other one
-Living With Sister Monochrome Fantasy: Just like for the 2 games above, this of is also a master piece, a mix between life simulation with you imouto + RPG! But be warned, despite being a very cute and light-hearted game, gaining favours from your imouto and the RGP side of the game are really difficult, even in normal difficulty. There will be some grind, but it's very funny and rewarding... just be careful to not push too much your poor little imouto or she might explode in rage against you and then it's game over. Ah and, this game is in black and white, feels like you're reading a manga... or actually more precisely a H3nT4i ^^. You can buy it from Steam, from kagura games official website and also DLsite. (PS: you'll also need the +18 patch if you buy on steam, it's free also from the kagura official site)
Adding about Living with sister... the author of the game is currently working on a enhanced version of her first game (named Living with sister monochrome ) with much better visuals and hand drawn animations this time around, plus new stories that were not present on the first game.... it's scheduled to be released end of this year first on DLsite, then steam through Kagura games publishing. She decided to name it. Living with sister Monochrome Encore
Honorable mention
-Summer clover: I found this one only on Steam... i never tried to look for it anywhere else. But it's a very good life simulation where you become the caretaker (or butler) of 3 beautiful sisters and you also take care a little bit of one of your co-worker (your Senpai more precisely) it's of very high quality and has live 2D nothing to say about it other than a excellent game very easy to play and very satisfying