...Well, that should probably be a part of it. [Can't forget the occasion, after all.]

Since it's from you, maybe you could include something about how you hope to become his friend? Get to know him better?

Or...something like that...

[...Yeah, she's not really sure. What would she write if it were a message from her? She hadn't gotten a chance to know Shinjiro all that well... hmmm...]