The main protagonist in Tegami Bachi. He is a 12 year old boy with a very focused mindset, regardless of what situations he gets into and always focuses on delivering the package. He was also born on the day of the Flicker. He's very emotional and is nearly constantly crying. He has a special gun called the Shindanjuu, literally the "heart bullet gun" where he loads a "fragment of heart" into the gun, then fires Akabari (Red Needle) at the target. He is seemingly being able to control the direction of the shot. His spirit amber visualizes memories of an animated object. As a child, he was "delivered" by the letter bee Gauche Suede, and was inspired by him to become a letter bee. He is searching for his mother, who was kidnapped to the capital of the country. His left eye is made of red spirit amber, allowing him to better use the Shindanjuu and also allowing him to fire a heart bullet from his own body. He originally has an antique from Campbell, though he receives the Nocturne #12, Gauche's gun. In chapter 29, after Sunny lost her heart to a Gaichuu, Lag's body glowed like spirit amber as he fired a special letter bullet at Noir (Gauche) in hopes of restoring his heart. His name is derived from "lagrima", a Spanish word for tears, "rag", "Lú" or "Lugh", the name of the Celtic god of the sun of the Danann family, and "seeing", the measure of sight.
His "Dingo" is Niche, a girl he saved from a Gaichuu (armored insect) who decided to stay at his side when he said yes to her asking him if saying goodbye would make him sad after seeing his memories via the Shindanjuu.His voice in the japanese version of the anime is Miyuki Sawashiro.