七支刀 [nanatsu-saya-no-tachi] or [shichishitou] in Japanese. It means the 'seven-pronged sword'. The 'seven-pronged' part of its name refers to the six protrusions coming out of the central blade. The real-Earth version of this sword is 74.9 cm long and made of iron, and is considered one of the national treasures of Japan. On the blade is an inscription inlaid in gold. Some of the characters on the blade are illegible (black block) and some are ambiguous (parenthesis), but below is what can be gleaned from it.
The Inscription
Chinese original
泰■四年十(一)月十六日丙午正陽造百錬(銕)七支刀(出)辟百兵宜供供候王■■■■ (作 or 祥)
先世以來未有此刀百濟王世(子)奇生聖音故爲倭王旨造傳示後世
English translation
"At noon on the sixteenth day of the eleventh month [May], fourth year of ■, the sword was made of 100 times hardened steel. Using the sword repels 100 enemy soldiers [Appropriate for the polite duke king] It is sent [bestowed] to the king. (Manufactured by or good fortune to…) [ ]"
"Never before has there been such a blade. The crown prince of Baekje's king, who lives under august sounds, had this sword made for King of Wa in the hope that it might be passed on to later generations."
Airborne Brigade

SR+
Type: Katana, Element: -, Growth: Slow, Cost: 28
Attack: 2,460 (lv1), 11,373 (lv120), 14,948 (lv150), 18,903 (lv180), 23,206 (lv210), 27,830 (lv240)
Defense: 2,410 (lv1), 11,144 (lv120), 14,647 (lv150), 18,523 (lv180), 22,739 (lv210), 27,270 (lv240)
Obtain: any chest that gives this rank
SR
Type: Katana, Element: -, Growth: Slow, Cost: 18
Attack: 1,490 (lv1), 6,883 (lv100), 9,050 (lv125), 11,448 (lv150), ? (lv175), 16,680 (lv200)
Defense: 1,450 (lv1), 6,695 (lv100), 8,803 (lv125), 11,135 (lv150), ? (lv175), 16,400 (lv200)
Obtain: any chest that gives this rank
All the Bravest
Stats: ATK +7, Number: 66, From: FF11
Equip: Samurai, Ninja, Auron
Drop: Kraken
Description: When not fighting for your life, this sword doubles as a great coat rack.
Category: Equipment