Episode 3 is the first one. After Kirino's father discovers that she watches anime and plays eroge, Kyousuke shows his colors as a Jerk with a Heart of Gold as well as a protective big brother by full-on defending Kirino and her hobby (after Kirino cried her eyes out about it at a local coffee shop), even threatening to kick his dad's ass if he does anything to keep Kirino from enjoying her hobby. Kyousuke even goes so far as to point out the friends that Kirino has made from having such interests. This whole ordeal will most definitely cause some tropers' eyes to tear up a bit.
And the exchange in which the scene culminates, as well as being hilarious, is grin-inductively awesome due to the subject matter and the over-the-top way in which Kyousuke delivers his message:
Kyousuke's father: You were in your sister's room, using your sister's computer to play a game about doing indecent things to your sister?
Kyousuke:It was really amazing. Got a problem with that? What's wrong with a high schooler having eroge? ... Iím not throwing this away! I'll defend this to the death!
Kyousuke: Listen up, old man! I like anime and eroge with a passion! I can say that I love them! If I throw this away, I won't be me anymore! Eroge are my soul! You hear me?!