The song's name is "July 14", the day is China's "Spirit Festival".
And this is an AU story. Jim and Sherlock met each other when they were children, but before long Jim moved to another city. They loved each other, so when they met each other again, they fell in love again. But suddenly came the car accident. Jim was injured, yet Sherlock was dead.
Jim attended Sherlock's funeral. He will never, never forget Sherlock.
Young Jim and young Sherlock are both played by Asa Butterfield.