What is the name of this anime?

A girl has a crush on her senior in the athletics club. And he is moving away. So she decides to tell him how she feels. She asks him will he be her first kiss if she can beat 11 seconds in her run(note this is all happening at night). She gives him her necklace which make a perfect rotation every second. And just as she was about to reach the goal a light appeared and a dude came out with a sword and armor saying where is the dragon (or something) and warns them that the dragon is coming and they should run. They don't the dragon shows up and after a shout from one the dragon starts to target the others (not the sword guy oh yah i think he's a prince or something) and chases them to a shrine where they think it safe for about 6 seconds and then the dragon shows up again and so does the sword dude they duke it out for a little while and then when they were about to finish the girl with the crush forsees the dragons last move about stabing the sword dude in the back with its tale and yels out watch out and the dude dauges and cuts it under belly and i think stabs the heart(mabey he just pulls it out one or the other) and takes the heart out of the dragon and it lights up while the dragon desinagrates. Then the sword dude and the girl talk for a little bit mabey 7 seconds and then the light appears again and take the dude with the sword and the girl both and they appear back in the dudes world. What is this anime?