She's trying to wash her legs, probably.

I like to think she is attempting to have a drink of water.

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I usually do that when I go to pool tho ... it's feels comfortable, and weird at the same time XD

Visunoriva said:

I usually do that when I go to pool tho ... it's feels comfortable, and weird at the same time XD

I mean, it's pretty comfortable position if one need to wash hair or just want to cool down their head, but considering that we talk about Seija then there's probably some reverse shenaningans in play and she's probably even try to dry her hair like that.

Naw, Seija is a full-blown contrarian, but that doesn't mean she'll do everything the opposite way.
I mean, she doesn't shoot herself when playing danmaku after all.