|The Melancholy of Haruhi-chan Suzumiya Part 4|
|Japanese title||涼宮ハルヒちゃんの憂鬱 IV|
|Air date||February 28, 2009|
The Melancholy of Haruhi-chan Suzumiya Part 3
The Melancholy of Haruhi-chan Suzumiya Part 5
Mikuru finds out that Yuki is viewing erotic images on her laptop, but is too embarrassed to tell what she's seen to Kyon. Several weeks go by, and several changes are noted. Kyon finds that the bookshelves in the room are being filled with video games, and Haruhi begins to notice Yuki wearing cosplay outfits. When Mikuru finds the outfits, a cosplay war breaks out. Meanwhile, Ryoko has revived herself, but in a foot-tall chibi form. Eventually, Yuki finds out, and after saving the miniature Ryoko from a hungry cat, allows her to stay with her at her apartment.
- Just before Mikuru finds Yuki's clothes, she can be heard humming Hare Hare Yukai, the ending theme of the first season of the main show.
- This is the final episode animated in CG. Starting with the next episode, the series switched to traditional 2D animation, likely to cut costs.