Heartwarming / Maribato!

• The fact that the characters open the duels with a "Gokigenyou!" tells you that none of the girls holds any ill feelings towards each other. Yeah, they're fighting, but they're also having fun in a safe and peaceful setting, showing that Lillian is, indeed, a great example of High School Rocks.
• This one overlaps with a funny moment, but it's very reassuring to see Yumi, an insecure Shrinking Violet in the light novel, being more confident. Yeah, her moves are funny and silly-looking, but, if her winquotes are any indication, Yumi is clearly having fun fighting and helping her Onee-sama (Or whoever she's paired with), fitting more with her Plucky Girl persona she gained via Character Development.
• A minor one: Kanako usually has a neutral attitude when idle, but... What happens if she's paired with Yumi? She looks happier and actually cheering for her, showing that she was having fun after all. Makes you wonder why Yumi didn't choose Kanako as her petit soeur instead of Touko.