Hello!! is a manga series by Daisuke Miyata. It was serialized in Shuukan Shounen Magazine (Kodansha).
Twins Aisaku and Asuma could not be any more different from each other. Not only do they not look alike, but their personalities are the polar opposites. While Aisaku's sole purpose in life revolves around making friends and not doing any school work, Asuma considers everyone around him as rivals, only in his way from becoming number one in every competition. Due to their extreme differences, each find the other repulsive and pathetic.
Out of sheer coincidence, these twins end up graduating middle school and being accepted into the same high school. Out of more sheer coincidence, their first day of high school ends up terrible due to one kid named Shindo. Shindo is a genius and ace rugby player, who plans on joining the high school's rugby team. Now, Aisaku and Asuma are both determined to beat Shindo in their respective ways.