I assume there was another discussion about bust sizes?

Specially since Seren broke that poor bottle in anger.

Wait a minute...*looks at post #1148918 isn't her real form about the same size as those 2?

I'm trying to make sense of the comment at the last panel. Is it because she chooses to have small breasts in order to have something to chase after? (since she is already and master magician)

As I understand it she enchanted herself with breast envy to keep a connection to humanity as time passes and she never changes.

Probably because it would be too boring to live eternal life without anything to be jealous of. Also, now post #1148918 makes sense - she doesn't want to turn adult completely. For the sake of having small breasts. Magician's logic, lol.
...Well, actually it's pretty well-thought, props to author.

Rakurakutei Ramen said:

Those who live forever naturally want to find ways to have fun to combat boredom. Seren's original form (which she calls her full power unrestricted form, or Super Mode) is a last resort, and for the sake of her current form of Kamishiro Seren, the only ones who currently know her in Super Mode are Tamaryuu and Master-chan. Or rather, because she got used to her current form, maybe... maybe she's not pretending and it actually bothers her. Yeah, it's exactly the same as when she the same age as her current form.

She said it herself when she changed back to her normal self... this is the state that she is most comfortable with. I can believe then that the breast envy was manufactured at the start but is 100% legit now.

Also, if we take her comment to the logical conclusion, Elza is a hermaphrodite by choice.

Oh, so that's why Seren reverted back to normal after actually gaining big breasts a few 4komas ago.

You know, i have to wonder if Elza is staying in that form purely so she can grope breasts in public while pretending to be innocent.

Aha! This was referenced all the way back from post #841548.

"Mine were really awesome when I was young" indeed. My continuity sense is tingling.