Yukari seems to be having the most fun here, and Eirin seems rather reluctant. What are they doing anyway...?

It seems like the bus game little japanese kids tend to play in, where they will march around while holding a long loop.

The reason Eirin is rather reluctant:
1) It's too kiddy for her. (She is a master to a bunny after all).
2) Those onboard the bus are ... *signal lost*

I take it that Yuyuko is bending over but Byakuren is the shortest? lol
but she still looks cute either way.
in fact they all look cute...