Ikuto's flirting is always the best, because he doesn't beat around the bush and just gets straight to the point. He doesn't hesitate to flirt physically, either, as he demonstrated with biting Amu's ear, placing his hands on her hips multiple times, ruffling her hair, etc. The reason Ikuto's flirting is so effective is because he treats Amu like a child. He knows that she's stubborn and likes to hide behind her 'cool and spicy' facade. When he breaks that facade, Amu effectively gets flustered, yet she has a lot more fun than she does when she's bundling up her personality inside. His flirtations are almost similar to the skills of a guardian character, he gets Amu to become a different person, the one that she wants to be. Ikuto is essentially teaching her that she is still perfectly good, 'cool and spicy' or not. He doesn't give Amu much support, though, with all of his disappearing acts. Even when he is there, he still acts jealous when she talks with basically any other which makes this ship a bit unhealthy.
Summary: Though Ikuto is a bit controlling when he gets jealous, this ship is pretty cute altogether and really brings out the best in both Amu and Ikuto.