Speaking of crossovers, Arcana Heart 3 Love Max!!!!! the upgraded arcade game from Examu lent a few characters to Agent Angels from Taito.
Arcana Heart characters show up as powerful enemies for you to fight in Agent Angels. Under certain conditions, you can get cards for Arcana Heart characters to add to your party. Heart Aino, Saki Tsuzura, and Scharlachrot are confirmed to be in the game.