待て待ているものは確認してから行くのを条件に追加しよう。

Riko is playing hard to get, she wants to go out with her onii-chan, but maybe not to a crowded pool where she might run into some of her school mates, maybe a river or the beach, of course if they were going out with several people then it wouldn't be just her brother that she was going out with, it would be the whole group so it wouldn't look like a date, although she wants to date her brother, Riko doesn't want it to look that way to other people, and it could be more fun with more people, basically Riko is being tsundere, thanks for the update.

これは、アレですね。
日向坂姉妹をブラパンツ持参必須を条件に誘うか？

梨子ちゃん、ｶﾜ(・∀・)ｲｲ!!