They must have gotten to one of "those" scenes.

"I'm in heat!"

"You were in your sister's room, using your sister's computer to play a game about doing indecent things to your sister?"

this is simply adorable :3

I wonder what are they seeing?

One can only imagine.

「おまえさ」「……なに？」「俺に会えなくて、寂しかったか？」「ばかじゃん？　なわけないでしょ……」「そっか、俺は寂しかったぞ」「……えっ？」ｼﾞｭﾝ
"Say" "......What?" "Did you feel lonely without me?" "Are you stupid? Not at all......" "I see. Well, I felt lonely" "......Eh?" (something like that)