Following the line of the precedent OVAs (of the same name) This anime goes around the normal lives of some elementary school (5th grade, 2nd class room) kids and their adventures, while turning to teens. Their games, stupid jokes, and the misunderstandings around their premature attraction to the opposite sex. Ryota Satou is the main character here, but his friends are almost as important as him since the school wouldn't be the same without them, especially the girls who the majority of time appear to be mature by their ages but in the ends they are as childish and even more "dangerous" than the boys. (Source: ANN, edited)

Second season of Mitsudomoe.

The 11-year-old Marui triplets could not be any more different. The oldest one, Mitsuba, is sadistic and kind of mature for her age. The middle one, Futaba, is perverted and very athletic and has the strength of a full-grown man. The youngest one, Hitoha, is generally very quiet and gentle but when push comes to shove, she might just be the strongest, the most perverted and the most sadistic out of the three. The three are all in the same class, led by the newly graduated teacher Yabe Satoshi. He usually gets pushed around by the girls and, on occasion, abused but the triplets also try to lead him and the new school nurse, the clumsy Kuriyama Aiko, together. However, Yabe had no intention of dating Aiko and the methods the triplets use to accomplish their goal are highly unorthodox...

Tokyo-born schoolboy Yukitaka Tsutsui is moving to Yamagata Prefecture for high school on a baseball scholarship. Since he went to the top middle school in Japan for baseball, the townsfolk are very excited about his arrival. However, when he arrives in his apartment, he encounters a strange man nonchalantly reading and wearing his clothes! The stranger claims to be an alien who crash-landed on Earth and has nowhere to go. Revealing himself to be Baka Ki El Dogra, the crown prince of the planet Dogra, he is just one of the hundreds of aliens that have already made Earth their home. Despite his regal origins, the prince is an infamous intergalactic fool who thinks nothing of inconveniencing others for his own amusement. Whether he is running ridiculous tests on his subordinates, giving strange powers to random children, or just generally being a nuisance, nobody is safe from the idiot prince's antics! [Written by MAL Rewrite]