Sasamaru

Sasamaru (ササマル) was one of the 10,000 players who were trapped in «Sword Art Online» and a member of the «Black Cats of the Full Moon», a small guild. He was killed along with most of his guild when a trap was triggered that, sealed the room, spawned numerous monsters into the room and prevented the use of crystals.

Aincrad Arc
Sasamaru, along with his guild, were found by Kirito in a Labyrinth, which was 10 Floors below the front lines at the time, retreating from a group of goblins pursuing them. After Kirito assisted them in defeating the monsters and indirectly offered to help escort them to the exit, the guild offered him a treat at an ale house in the town. When Kirito was invited into the guild there and agreed to the invitation, Sasamaru, along with the other guild members, officially welcomed Kirito into their guild. Afterwards, for about a month, due to Kirito's coaching and assistance, all the guild members leveled up at an extraordinary rate for medium-level players. At some point, he along other members of the guild were shown battling against a Killer Mantis in the anime. One day, when the guild leader went off to purchase a home for the guild, some of the members suggested hunting in a higher level dungeon to earn more money before Keita comes back. After an hour of battling, they had attained the target amount of money. But then, the thief of the party discovered a hidden treasure chest, the trap difficulty of which was slightly higher than in the other areas of the dungeon that they had been in. As the thief lacked the skill level to disable the trap, an alarm was raised, the room was sealed in with an active anti-crystal field and numerous monsters started spawning into the room. Sasamaru was killed in the battle along with his guildmates, except Kirito.