In 3, after picking Glycine as subcommander, she decides that Ogami is a worthy groom for her. Cue the maids suddenly hogtying Ogami up, even carrying him off like a captured wild boar in one scene! Even Glycine's head maid approves of her choice.
During chapter 2 of the 3rd game, we have Erica's reasons for wanting to go to the circus:
Erica: The circus is a very wonderful place. There you will find dreams...and hopes...and love...and a human cannon.
In the 3rd game, we have Sakura, Sumire, and Iris's reactions to meeting Erica:
Sakura: Ogami, is Erica...
Sumire:...Always like that?
Ogami: Yeah, she's always like that.
Iris: Onii-chan, you've got it tough, huh.
During Kanna's section of special training in the 3rd game, she warns the Paris Kagekidan members that the paintballs will hurt if they shoot themselves. What does Erica do? She bombards herself with paintballs, just to see if what Kanna's saying is true.
and Ogami's reaction to it.