When Mayumi says her sister is clueless, she often doesn't know how clueless she is herself.
Hanamaru seems to tell a very real story too. In fact, girls in the real world are actually very often clueless. It is either them waiting for you to be the one to confess to you (what do girls have against themselves confessing anyway...?) Or that they really decide to not think about it, instead of sincerely thinking that you're a really nice guy.
Then again, girls are weird in the sense that every boy around them is either friend or boyfriend material to them. When friend material falls in love with them and does all sorts of things for them, they like them even more... as friends.
And when boyfriend material passes by and doesn't notice them, they chase them all the way to where the sun sets. Aah. What a tragic yet colorful world. Hanamaru spells it all out nicely and if you don't notice that, you're either preadolescent or pretty clueless too.