The second half of the third Parallel Works, which details how Nia met the Dai-Gurren Brigade in this universe. And as an added moment of heartwarming, Kamina is still alive when it happens.
The growing bond of the Rangers throughout the entire story is very endearing.
The budding romance between Shinji and Hikari is extremely awkward for both characters(Especially with no thanks to their teasing peers), but it's a genuine chance for happiness that the Eva Pilot becomes more and more willing to take. Hikari cements their relationship with a Big Damn Kiss in Chapter 24
Roger's interactions with his daughter and even Dorothy, his wife.
Shiro standing up for Noriko after she's discovered to be a cyborg in Chapter 25.
The sisterly bond that the Love Interests of the rangers share with each other. Especially when the older ones encourage and look out for the younger girls.
Believe it or not, Kaiba still clearly cares about Mokuba despite outward appearances. Look no further than this exchange in Chap. 25 when Mokuba initially thinks that Seto is dead.
"Is my little brother crying? I thought you wanted to run my company?"
"After I win it from you fair and square big brother!"