The manga is not bad really but it had potential to be better which was a let down. It seems like a thought just put together on a whim. The main girl's background and the plot itself seemed poorly put together. The characters needed work and the story progressed too fast.
The main girl Rio doesn't have any redeeming characteristics and was a bit annoying. She seemed kind of stupid as well, her little brother, Minoru, seemed to know more than her. Lancelot was her lover who came out of a card. He seemed like a gentleman at first, like how he is portrayed in
legends but after he realized his feelings for Rio, his personality was off and he acted not like the gentleman he was. The card was not explained and the reason why Lancelot can't stay seemed logical but the conditions in which he can stay, wasn't so much.
The only good characters are Minoru, who seems to get pushed around by Rio and Lancelot. He is always being used in their schemes. The other good character is Yuuki who likes Rio. He is kind and although he was pushy at first he redeemed his character later. He also seems to get used by Rio and Lancelot.
The story could have been better, so I am kind of disappointed.