Episode 43. After an endless cycle of misunderstandings, confusion, and heartbreak, Keitaro and Yuka finally realize that each is the one the other has been emailing for the entire series. This goes hand in hand with Keitaro seeing Yuka forced to transform into her Orphenoch form to fight Saeko. Once the battle's over, Yuka stands there, ashamed and afraid that she's going to be rejected yet again... and the episode ends as without a word, Keitaro simply hugs her from behind.
This Tumblr post features a lot of pictures of the KR555 actors doing silly things.
The Complete Selection Modification - Kaixa Gear video has Kusaka's actor, Kohei Murakami, checking out a realized version of the Kaixa belt and weapons his character used in the show. He even cleans his hands with a hand wipe before checking out the belt. Kohei's excitement is very palpable here.