I guess she felt she was too similar to his actual little sister, so she went the 'exotic is superior' route?

elgee said:

I guess she felt she was too similar to his actual little sister, so she went the 'exotic is superior' route?

But the previous image shows that it's just a façade and she can go back to "plain imouto" if she feels it'll excite him more.

I kinda figured it was a simple "high-school debut" thing.

The image the blonde was introduced in called her a "new friend," but they clearly knew each other before...Maybe she switched back to show the brother who she was?

Miscellany said:

The image the blonde was introduced in called her a "new friend," but they clearly knew each other before...Maybe she switched back to show the brother who she was?

Yeah, this must be it