Lets Cofan is one of the three orphans brought aboard White Base during the One Year War. While aboard the ship, Letz, Katz, and Kikka became a combination of mascots and troublemakers for the ship, and were involved in several incidents. Following the One Year War,

Spoiler

Letz was adopted by Hayato Kobayashi and his wife Frau Bow, along with Katz and Kikka. The three visited Amuro Ray's home in Cheyenne, Wyoming before continuing on to Japan. He stays close to his adopted mother, helping her with the unborn child Frau is carrying.

(Source: Gundam Wikia)