He watches Kanji deal with the whole boob-in-the-way situation with a mixture of sympathy and unrepressable amusement, and does his best not to snigger because he doesn't want to make Kanji feel even more uptight about this whole thing than he already is.
He's also trying hard not to tell Kanji he make a rather cute girl.
"So, what - you swapped clothes? Were yours big enough for him? How tall is he today?" He's kind of imagining King Kong striding above the skyline tall and wondering how he's managed to miss Nico all day!