Paula's snipe about Chitoge just 'playing around'... yeah, no... maybe at the start that would be a good excuse, but she's legitimately fallen for him and fully acknowledged it, now. For Chitoge's part, it's definitely serious at this stage. It's on Raku to return those feelings, whenever he realizes how much he actually cares about her. Which will probably be much closer to the end of the story.
Anyway, Raku sees right through Paula's motivations. You know, when it involves observing other people, it's so much easier to see what's going on than if you are personally part of the situation. It's something us readers can struggle with reading these stories. If you're not in the situation the characters are in, you have no idea the pressures and factors involved in them not being able to understand what is going on and do the sensible thing. A little sympathy and empathy goes a long way.
And Seishirou coming to grips with how much she hates the thought of someone else kissing Raku. She's starting to understand what it is to 'love', and the fire that jealousy can set in your heart.
Love her solution to the problem of 'kissing' Raku, though, when she knows she must let Chitoge have the honor (not to mention her own discomfort with doing it properly). So cute. "She's such a child."
