Best Friend and a Girlfriend,Who's the Third Wheel?

S1, E6: Maki knew that Yo and Ren planned to go camping and decided to join. Yo found about that Ren and Maki were dating, shocked that Ren couldn't tell her himself. While Yo became unable to enjoy this camp anymore with Maki's jealousy on site, Maki was unhappy with Yo being too closed with Ren.