Rinne no Lagrange Season 2

How should I put it.... I'd say its sort of like a hardcore version of Rinne no Lagrange Both are Original Work: New + Same feelings of emptiness + Sci-Fi + Really good opening/ending + The main character also faces the problem of being the only member of his school club + Parallel Universe + The main characters from both series would rather not pilot robots and fight but they do so in order to eventually preserve peace + Main characters (Kyo and Madoka) fight to protect their hometown + Slow paced + Fights between friends + The story of a tragedy is retold more than once throughout both series; at the END the tragedy repeats itself. + An unknown girl from out no where comes to earth, shows up at the high school and gets the main character to pilot a special type of robot. + Madoka and Kyo are both athletic and like to swim; have been in a swimming competition and only lost because of an unexpected interference. + Both series take place in the Chiba Prefecture of Japan a real-world location near the ocean + Flowers are prevalent in the themes of the show; being able to see/touch them determines a sense of peace and hope. + read more 

Both of these anime (even though the rinne im recommending is season 2 i suggest both of them) are a big part of forming bonds and friendship with people that are different. They are both also set on planets that are mostly water. Both anime have mecha. 

The mecha are piloted by children in order to protect the planet.