Found the answer myself: the logo RMC on its cover stands for Ribbon Mascot Comic, a shueisha publisher shoujo comic for 8-14 yo girls. Turns out the author is under RMC.. Another sister comic: MC-Margaret Comic for 11-17 yo girls and Betsuma-Bessatsu Margaret for 15-21 yo readers.
That's why it is a story of middle schooler.. ╮(￣▽￣)╭
Didn't notice they were middle- schoolers ! ! Ugh ! When these guys graduate from middle school, then go to different high school, alas, goodbye sweet , pure love. It's rare to survive middle school , then high school, then college, and still be together.
The summary says high school, but in the chapter where yuugure chatting with his friends, he said 2nd year of middle school, and after that continue reading it kinda feel uncomfortable for me. Like reading illegal underage love story that won't last until graduation since they are still, you know, brats. Why not make it a high school story?? Why??? Tama and the gank can be a college students just fine, so WHY?? I can't figure out the reason, it's really bugging me...#－.－)
However, good story, nice characters. For the plot, well so far it's good, but the couple will finally encounter their first problem, so let's see.