Bong-Seon (Kor: 봉선) is the National Treasure of Yu Mi-Ra. This national treasure is a sword. It was stolen by the Organization but was retrieved and returned to Yu Mi-Ra after she successfully passed the National Treasure Certification Exam.
Before it was awakened it looked like a typical wooden sword used for training. When awakened it took the form of a long sword with the Ying-Yang sign at the hilt but later changed after she recovered the sword, It now appears to resemble a red thin katana.
It has the normal abilities of a sword and like most National Treasures it is impervious to Charyeok attacks and can give the user more destructive force, among other abilities.
- Teleportation: It is capable of teleporting to its owner. It appears to have no set distance and will appear either when called or needed.
- Levitation: It has also been seen levitating and coming to its owner on command.
- Attack Enhancement: It is capable of enhancing attacks and cutting through powerful Charyeok easily. It is also capable of blocking extremely powerful attacks.
- Charyeok Amplification: It also amplifies a person's Charyeok but this function can only be used three consecutive times for an unknown time period.
- According to Wikipedia, Bong-Seon is actually a Korean National Treasure. It's was a stele of the the Bongseon Honggyeongsa Temple.
- Bong-Seon means "In Reverence of Father's Wishes", fitting to Mi-Ra's character especially in the first half of the story where she felt like she had to carry the burden of her father's wish to find a worthy successor of the Moonlight Sword technique.