You'll have to not get the full 8 points on the scale with Sol, I imagine keep it lower than 8.
Forgive me if I'm not 100% sure, but this is just by speculation and the fact I got it but don't remember the steps entirely.
When you choose to skip school with Hyugo and Sol, go to the arcade, get any of the two plushies but the horse one, you can choose to thank Sol if you want to. As long as you score under 8, Sol will choose not to take you home so Hyugo will escort you home instead. After MC goes to bed, this cuts into the NSFW cutscene of Sol breaking into MC's home.
Don't quote me on it, just wish to help and I hope it does. Happy CG hunting.