Yona of the Dawn. Volume 1: Mizuho Kusanagi

A red-haired princess loses her family and her kingdom… Now she must rise and fight for her throne!
Princess Yona lives an ideal life as the only princess of her kingdom. Doted on by her father, the king, and protected by her faithful guard Hak, she cherishes the time spent with the man she loves, Su-won. But everything changes on her 16th birthday when tragedy strikes her family!
Yona reels from the shock of witnessing a loved one's murder and having to fight for her life. With Hak's help, she flees the palace and struggles to survive while evading her enemy's forces. But where will this displaced princess go when all the paths before her are uncertain?