I hope this is still an active case, seeing as how nobody has contributed to it in awhile, and the OP didn't mention anything about the case being solved on the thread. I just saw this case tonight, and was intrigued by it. I had a few deductions (may not be perfect) and many questions, but I am still not 100% sure if my guess is right.
Regarding the First Murder,
+ In the second murder, it was said that the victim was attacked from behind. Can the same be said about this case?
+ How far away was Tsu An Jan's home from the scene of the crime?
+ How far away was Kurei Nana's home from the scene of the crime?
+ Does it matter where exactly the blood was found on the jacket?
Regarding the Second murder,
+ How far away was the birthday party from the crime scene?
+ What about Kurei Nana's alibi at the party? Is the absence of other students confirming her continued presence a part of the hint?
+ How reliable is the alibi of Kanda Jirou? Considering that it came from one of the suspects, as well as a bunch of drunk students (and one other sober student).
+ When did Shiro Atsushi and Tsu An Jan's 3-day trip out of town end? Or was their trip ended early because of the second crime being committed?
+ Why would the victim decide to meet someone alone, and not tell someone where they are going? The victim must have trusted the perpetrator enough to meet the person without telling anyone, despite the fact that they could be the killer.
Regarding both murders,
+ Does it matter how the time of death was determined? Not sure if the cold weather would have slowed down rigor mortis, but this is a possibility (a trick!)
My deductions:
Kanda Jirou
Yamada Mikan
Tsu An Jan
Kurei Nana
Shirou Atsushi
What I still don't understand...
+ Kanda and Yamada were both singers, which might reference to the bloody message on the third crime's note "mother crow cries" as someone else mentioned. It might also reference the fact that the crow is black, a reference to the color of Tsu An Jan's and Shiro Atsushi's hair color.
