I can't read the kanji in Mystia's first (off-panel) bubble. Can I get some assistance?

There's a bit of mistake in Rumia's phrase as well. What she says means something like "In the past your breast was about a palm big", and Mystia reacts with "When did you get to touch me, you %insert a mildly sweary word%"

ThunderBird said:
I can't read the kanji in Mystia's first (off-panel) bubble. Can I get some assistance?

I think it's a stylized い

CyrusVorazan said:
There's a bit of mistake in Rumia's phrase as well. What she says means something like "In the past your breast was about a palm big", and Mystia reacts with "When did you get to touch me, you %insert a mildly sweary word%"

Hence the check_translation tag. I never get the persons right in Japanese, given their usual omission of personal pronouns. So thank you for the correction!

If Rumia wants bigger breasts, then she should get Mystia to remove her ribbon.