It's the trailer of a doujin PC game called "the Rhyme of a Love Song", RLS for short. Characters are originally from the Japanese game series "La Corda d'Oro" .
The game has been released on August 17, 2007.

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Translation:

What kind of meeting it is?
From strangeness to familiar.
What kind of destiny it is?
From acquaintance to dependence.
Use your fingers,
to play the tune of your heart.
It is not simple notes;
it is the melody of Love.

No matter it is sweet,
Or it is bitter and sour.
with the notes of songs crowding around,
Feeling,
Those...
Graceful happiness (of love)...

(Male voice speaking in Japanese)
I'm here waiting for you.

Open the door of
The most beautiful love of this summer.
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Producer's Forum: http://corda.5d6d.com/?fromuid=3

Install-less Game Package:
http://aydearsmirage.crblog.org/user18/87923/archives/200... (less info)