Responses
He want to know what 'love' is through his own perspective and words but he never felt it before. And he doesn't understand the 'love' that other people is portraying and expected from him.
Singing; I wanna know what love is... I want you to show me... dun dun.
I'm seriously stunned he's been mulling over on a very deep analysis on what love is. I kinda understand him, his point of view: people really do throw the word "love" around so easily. However it's only related to "romantic love" because I do believe people can love someone unconditionally, but falling in love? That's another thing entirely. And on that note how can you be sure you've fallen for that person, how do you decide that your feelings can be defined as "falling in love". I remember that in "Kimi ni Todoke" there was this nice take where the protagonist actually first admires the male protagonist. Only later she realizes that it's love. I think this fine line between feelings and the fact that each person has their own take on what is love is the key. So basically I think you fall in love when you decide to do it, in a way.
However, I suppose uke here is actually just kinda scared- Usually when you bond with someone and that person finds out other sides of you they don't like, well it's either "I can accept/avoid your 'ugly' sides" or "You're no more the man I first fell for". That's why maybe he believes love is too shallow if all that takes to fall out of love is just that.
And the fact that people have this romanticized vision of love just creates more misunderstandings/problems in relationship- However it is I'm seriously loving this manga a lot.