yeah, you're right, It seems to me that they rushed the progress, decided to use chibi animation instead of full-body animation to shorten the time, didn't know why, but it was a damn shame, there was even a big flaw that it's impossible to get the 5 girls ending because there's not enough time to build relationships and stuff, so they added the orb thing to help players to advance to all the ending.
The reason for chibi was indeed to spend less time which is why the main girls only had them for major scenes. There was more planned but yeah they ran into more issues than they previous thought.....so the first release didn't even have a complete game (ended at day 5, no scenes for side girls, no NTR at all). So they slowly added in stuff over time.....but stuff kept breaking when they did. So they had to spend time fixing, then updating, then fixing.....finally they ended with 1.05.....but it was still impossible to get harem or full NTR. And sadly, had they just changed a few things....it would actually be possible to do.
Overall: lower starting affection to 30, thus erasing the need to interrupt and manually lower it.
day 1: Have Izumi gain development when she plays with her own breasts. Give Airi an evening scene thus making it possible to have sex with her day 1.
day 2: No real changes, except add some extra animation if you've already had sex with Airi or Toko.
day 3: An requires way too much attention, if made like the other girls you could start her this day instead of day 5. If day 1 was changed, could start Izumi's scenes in morning. Give one of An's scenes to Kano.
day 4: Make every scene interruptible! And for NTR, have it so that the side girls start this day if they have stats as well. Finally have NTR scenes play for both girls present if both satisfy conditions.
day 5: A good day really. Since Izumi started scenes earlier, you can give Kano one of her scenes.
day 6: Have all side girls NTR start on evening if conditions are satisfied. Give MC ability to interact more with girls if interrupted.
day 7: no changes needed.
day 8: Side girls take out the need to choose if you're having sex with multiple girls, also make all NTR scenes happen for girls who qualify.
day 9: No real changes, balance out girls who fall behind the others in scene counts.
day 10: Actually be available through normal means. Have different things happening depending on overall actions (Harem, all NTR, single girl won, single girl NTR)
day 14: If won Airi and Toko, have 2nd date day where you can choose girl you didn't choose on day 7.