Tamasaburo

Tamasaburo was a Felinoid Assassin and the guild master of Cat Food, the guild Nyanta was in before it disbanded after his sudden disappearance.

Like Nyanta, he began playing Elder Tale during its open beta period. While Nyanta was still a novice player, Tamasaburo invited him to the guild.

However, he suddenly stopped logging into the game one day, and the guild eventually broke up.

Log Horizon: Nyanta's Fortune Recipes
Despite having left the game long ago, Tamasaburo suddenly reappears some time after the Catastrophe, running into Serara in Akiba. However, he doesn't reunite with Nyanta until Nyanta dies during the Shibuya Raid, where Nyanta meets him on the beach before reviving.

There, it is eventually revealed that the Traveler possessing Roe2 is temporarily using Tama's body for some reason.