Pretty sure it's the artist, because it's on her ring finger in the panel right before that.
But you can easily headcanon it as Arisa being a dork, since she's fiddling with the ring on the next page.
Although would she ever take off something given to her by Mari?
Damn I was really hoping Arisa give Azusa a passionate wedding level kiss that end up seducing the little sis into her charms! Having young and old sisters after her is just awesome for her eyes!
Mari introducing her wife as her roommate to her own sister made me feel strangely sad. Don't be ashamed of your marriage, Mari! I thought you were past that now, at least with your family.
She looks like the last boss in their relationship!!
Arisa... don't screw this up! (more than what you just did lol well the sister was being really inconsiderate too)
There was a time when this manga started as an all-fluffy story. Now it's getting lewder. I don't mind it at all though; but I missed the atmosphere of the first half of this story. Arisa's still awkward but plain lewd. Anyway Mari is BEST GIRL