Tiger Honor (Thousand Worlds #2) by Yoon Ha Lee

Sebin, a young tiger spirit from the Juhwang Clan, wants nothing more than to join the Thousand World Space Forces and, like their Uncle Hwan, captain a battle cruiser someday.

But when Sebin's acceptance letter finally arrives, it's accompanied by the shocking news that Hwan has been declared a traitor.

Apparently, the captain abandoned his duty to steal a magical artifact, the Dragon Pearl, and his whereabouts are still unknown. Sebin hopes to help clear their hero's name and restore honour to the clan.

Nothing goes according to plan, however. As soon as Sebin arrives for orientation, they are met by a special investigator named Yi and his assistant, a girl named Min. Yi informs Sebin that they must immediately report to the ship Haetae and await further instructions.

Sebin finds this highly unusual, but soon all protocol is forgotten when there's an explosion on the ship, the crew is knocked out, and the communication system goes down.

It's up to Sebin, three other cadets, and Yi and Min to determine who is sabotaging the battlecruiser. When Sebin is suddenly accused of collaborating with the enemy, the cadet realizes that Min is the most dangerous foe of all...