The authoer definitely put a lot of work into the pixel scenes. A lot of variations than most other pixel games.
Personally I feel the overall tone and atmosphere of the game is on the lighter side. Whether good ending is easy to obtain or not I think would depend on how you define good ending.
For example, one ending is NTRS where you are actually happy to share your GF with the dude, and he treats you like a good friend whos sharing the same toy/hobby (your GF). Is this happy ending? I mean everyone invovled is kinda happy? Of course, there is harem ending as well.
I believe there are 8-9 endings in total, and looks like save files & guides are posted here to help you, so I'd definitely recommend you giving it a try if you dont mind using a guide.
Oh i needed to be more specific there my bad, good ending would be harem ending or one ending that i can get back my GF, im not fan of Sharing/Netorare/Netorase
Another thing that interested me is the "Steal the Rival's girlfriend" since im a netori fan, so a ending like that i would like to pursue too
For the sex sprites, its majority the Rival x GF or the MC have a good amout of sex sprites too?
Edit: Dont need to anwser, i tried the game myself for around 15 days, it was really slow and most sex scenes are between the rival and GF like i imagined and before i can do anything to stop the rival they'll bang my GF in anyway possible
i thought with the blonde girl could balance the amount of sex scenes but not sufficient to be invested in the game, also the "you cant satisfy me" always is a turn off. A pity because the sex sprites are really good.
Gl to the NTR enjoyers, not my cup of tea but the game can be a diamond if you like Sex sprites like me