I don't get it.
Is she afraid to see Kyon in a yukata because it might make him irresistable to her?

I think she doesn't want Koizumi in one.

Wouldn't she be guarding him instead of hiding behind him then?

Ralen said:
Wouldn't she be guarding him instead of hiding behind him then?

She probably knows that she wouldn't be able to defend him from anyone, which is why she's clinging to him like that. It looks more like she doesn't want him to go through with it.

I think she's pushing him. Obviously in this artist's world, these two are a pair. So it's only natural she would want to see him in one, right?

DoubleT said:
Obviously in this artist's world, these two are a pair.

It's called shipping.