Osoi

was a genin-level shinobi from Kumogakure who once fought alongside Toroi. He was also the father of Musai.

Background
Osoi fought alongside Toroi in his last battle, which lead to his own death. He was later mistakenly reincarnated by Orochimaru in an attempt to reincarnate Toroi. After explaining the mix-up to Orochimaru and Kabuto, they decided to keep him around for future use.

Personality
Seemingly a very proud ninja, Osoi told his son that he should lie about his father's ability. He wanted Musai to ensure that the Raikage knew of his sacrifice. While he is a proud individual, he deeply respects Toroi and his former partner's superior abilities.

Abilities
Osoi displayed no unique combat ability, but his son Musai stated that he didn't even make it through the chūnin exams. Still, he fought alongside one of Kumogakure's most famous ninja.

Fourth Shinobi World War: Confrontation
During the Fourth Shinobi World War, Kabuto deployed Osoi, who he saw as one of his weaker assets, in an attempt to unseal his other, stronger pawns. During a scuffle between Kabuto's weaker pawns and the Allied Shinobi Forces, Osoi spotted his son Musai. After they talked for a while, Osoi was sealed.

Fourth Shinobi World War: Climax
Later, when the Impure World Reincarnation Technique was cancelled, his soul was returned to the afterlife.

Trivia

 * literally means "slow" or "late".