Hoshimaru (ホシ丸): Shiina's companion. He does what Shiina unconsciously wants to do or have happen. This means that in reality she does not wish to casually speak with him, and that everything he does is actually Shiina's will - whether for good or for bad.
In the anime it is not stated, but later in the manga it becomes known that Hoshimaru is Takeo Tsurumaru's dragon, not Shiina's, which explains why she could not link with the creature. When Takeo dies, Hoshimaru attempts to turn his bearer into a virgin princess, but somehow fails.