Why does he think he's so important
Knowing that I like to eat pizza quite often, you went and did a promotional event for Pizza Hut. You even picked a very cute design with the agreement of your colleagues and staff members. In fact, you even had to work extra hard and over time for it as that you were already very busy and that your schedule was quite filled up already. Now that I realized it, I really want to eat at Pizza Hut together with you.
More at http://myanimelist.net/blog.php?eid=67910
You see, every thing that Mizuki Nana does, from which promotional campaigns to which anime she decides to act in, to which clothes she wears and which games she plays, all happen to be things that this guy likes.
Actually, the real reason is that Nana knows all about Kira01's tastes to the point that she's stalking him, and she does all these things in public because she wants to send him a secret message that she is obsessed with him too. BUT NO ONE ELSE UNDERSTANDS THIS SECRET MESSAGE but him.
When I voiced support of a political party, its approval rate goes up automatically. When I voiced disapproval, its approval rate drops drastically.
Basically... it's a matter of causation vs correlation. This guy sees all these things that happen ("I like Pizza Hut... Mizuki Nana did a Pizza Hut campaign") and assumes that because they both happen, one must cause the other, and therefore he draws some conclusions.