Teto is cheerful and eager, though may be naughty at times, perhaps inspired by her mischievous roots from Doraemon. Depicted also as a Tsundere (a mannerism that feigns disinterest to people she is attracted to). She hates people who think her pigtails are actually drills. She also can be narcissistic at times and loves getting attention. She gets very angry or sad if someone has bread and does not share with her. She won't always talk about bread though.
Her age depends on your story.