This is an AMV for the song "Miss Parallel World" made by the band Soutasei Riron, the video itself called The Tender March is made by Wataru Uekusa. This was a very artistic eyecandy, I loved the visuals, very special :) Most of the time quite cute but has some more dark undertones especially in some scenes. The song was good and catchy but what about the plot? Well the video seems to have a deeper meaning than just being eyecandy for the music. It seems to be a girl who grew up as a very imaginative girl who looked at the world very different, being in asomewhat parallel world. As she grew older her detachment from the world have made a lot of problems for her, she tries to ignore this parallel world without succeeding so she starts to fight it.
Whether or not it means she came to terms with her imagination or she grew up from it, I cannot really say ^^ There is a lot to interpret