An inscription on the side of the blade is an important source for understanding the relationships between kingdoms of the Korean peninsula and Japan in that period.
In the past, the material was considered to be forged mild steel from the state of fracture surface,[4] but the theory that it was cast became the mainstream through the latest research by Tsutomu Suzuki and experiments to create replicas by swordsmith Kunihira Kawachi.
The following is the original Classical Chinese text; 則獻七枝刀一口 七子鏡一面及種種重寶 仍啟曰 臣國以西有水 源出自谷那鐵山 其邈七日行之不及 當飲是水 便取是山鐵以永奉聖朝[11]In English; :(52nd year, Autumn, 9th month 10th day.
In English: First Side: "At noon on the sixteenth day of the eleventh [fifth] month, fourth year of Tai■, the sword was made of 100 times hardened steel.
[13] But that era name, Taihe, was never written as 泰和, but 太和, so with the ambiguous 2nd letter, this puts this traditional theory in dispute.
[15] Furthermore, the creation of the sword being on the year 369 is solely based on interpreting the "泰■四年" inscription as "泰和四年" yet also leaving out what comes right after, the 十(一)月十六日丙午正陽 which means "At noon on the sixteenth day of the eleventh [fifth] month."
[citation needed] In 409, Wei's envoy visited Baekje, and King Jun-ji extended hospitality to him, so that sword was formed by 408.
Kim notes that the sword uses the term "候王" translated as "enfeoffed lord," and thus claimed that the Wa king was subservient to the Baekje ruler as could be seen in 6th and 7th centuries, 3 times the Wa were conscripted for Baekje's wars against Silla (554, 562, 662) but never the reverse, even for its final battle in the Battle of Baekgang and its subsequent aftermath of building Korean-style fortresses in Japan.
The former interpretation indicates that the phrase "奇生聖音" has a Buddhist or Taoist nuance, and that the bestower has "lived under august (holy) sounds".
Ueda Masaaki (quoted by Saeki, 1977) is rather an exception among Japanese historians because he “has maintained that the Seven-branched sword was ‘bestowed’ on the Wa ruler by the king of Baekje.”[citation needed] Ueda “based his interpretation on the argument that the term ‘候王 koo’ [huwang] appearing in the inscription denotes a ruler in vassalage to the Baekje king and that the inscription is written in the commanding tone of a superior addressing an inferior, exemplified by the sentence reading ‘Hand down [this sword] to [your] posterity."
However, Saeki (1977) argues that one can not interpret the inscription to mean either “to bestow” the sword on the King in vassalage or “to respectfully present” to the emperor, as many Japanese scholars have maintained since the Meiji period.
Saeki seems to be inclined to take Hirano's argument that the inscription simply indicates the fact there was a respectful and sincere relationship between the rulers of Baekche and Wa.
[21][22] Yet another theory proposed by Kōsaku Hamada of Kyushu University suggests that the original seven-branched sword was created by Eastern Jin in 369 (泰和四年 4th year of Taihe) for a vassal lord with the first inscription.
The king of Baekje ordered the creation of a replica of the sword with the second inscription and sent it to Wa for an alliance as peers under Eastern Jin.
Even if 泰和四年 is the correct theory, using Chinese era names as standard was a common practice around East Asia at this time.
[citation needed] Regardless, the sword proves there were very close ties between the Baekje and the Wa, and the opening of friendly relations between two countries probably dates to the year 372.