In both dramas there are time travel to be able to save and win the first love.
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In both dramas you travel to the past through photographs in order to conquer your first love........

In both dramas you travel to the past through photographs in order to conquer your first love.......

In both dramas you travel 10 years into the past to meet your first love again...........................................

In both dramas there is time travel: in Blue Birthday by burning a photo, in Nine by burning a stick of joss.

Both stories are about two boys who write songs and are helped by the female protagonist.

Both stories talk about two bands of young boys who want to make their debut as musicians.

In both dramas the protagonists have been friends since high school. They have feelings for each other but their timing is always bad.

In both dramas the protagonists have been friends since high school. They have feelings for each other but their timing is always bad.

Both female protagonists are shy and lonely at first, but manage to make friends with the help of the male protagonists.

In both dramas, the protagonists think they are half brothers and one of them interrupts their story.

In both dramas a male student falls in love with his female teacher.