Episode 312
Something strange has happened to Dororo: he seems to have turned back into the scary Assassin he used to be! Later, Koyuki seems to have a scary secret. Her friends all gather together to spy on her and figure out what it is! Source: crunchyroll
Aired 01/05/2010EP 312 - Episode 312
Sgt. Frog
Keroro is a frog-like alien sent from his home planet on a mission to conquer Earth. But when his cover is blown, his battalion abandons him and he ends up in the home of the Hinata family. There, he's forced to do household chores and sleep in a dark basement that was once supposedly a prison cell haunted by the ghost of an innocent girl. He even spends his free time assembling Gundam model kits. During his stay, Keroro meets up with subordinates who were also stranded during their failed invasion.
(Source: Anime News Network)