The Highs and Lows of the Lovemeter

I've got to do something about my crush, Marika's completely broken lovemeter. First, I figured I should get along with Toyotomi, whose lovemeter is low, but she treats me so harshly, I get discouraged quickly. However, after school, when I help a crying girl at the usual park and take her home, it was Toyotomi's house?! Apparently, the girl was Toyotomi's younger sister! As soon as she invites me to have dinner together as thanks, her lovemeter goes up...