Mello is the older of L's two successors raised in Wammy's House, Watari's orphanage for gifted children, in Winchester, England, United Kingdom. Similar to L's fondness for sweets, Mello is often seen eating bars of chocolate. Mello has an excellent mind and that he sometimes lets his emotions get in his way.

Spoiler

Instead of working alongside Near to discover Kira after the news of L's death, Near, Mello refuses, citing an inability to work with Near, to whom he is considered second. Mello instead decides to find Kira his own way, joining the Mafia.

Mello is the narrator of the spinoff novel Death Note - Another Note: The Los Angeles BB Murder Cases.