There is a Japanese pun here that won't make it across to English -- Shinichi is saying す repeatedly, but it's obvious he's not finishing the word. す is the first syllable for both sukiyaki (a type of food) and suki (which means "to like". In Japanese, it's sufficient to just say "suki da" to someone you like to let them know.)
So when Shinichi says: すき... やき を 食べたい! suki... yaki o tabetai!
(食べたい = tabetai = want to eat)
He's trying to confess, but chickening out.
Maybe a closer tranlation would be something like: "I like y... yakisoba!"
