Tōtōsai, whose name translates to "Sword Ceremony-Preparer", is the old man who created the Tenseiga, the sword of Sesshōmaru, and the Tessaiga, InuYasha's sword. He was a friend of InuYasha's and Sesshōmaru's father (Inu Taisho), who entrusted Tōtōsai with helping his two sons master their respective swords. He knows very well the techniques that the swords are capable of and he is somewhat disappointed it takes InuYasha so long to realize and control the Tessaiga, while amazed how Sesshōmaru masters them on the first try. He is often absent minded and will abruptly forget what is happening, much to InuYasha's annoyance. He occasionally argues with InuYasha on how he uses the sword, and scolds him for his misuse of it and throwing it away at times in battle. When he first meets InuYasha, he battles him to test if he should be the one wielding the sword. He is a pyromancer and has a rather long hammer, which he, along with his pyromancy, uses to makes swords or repair them.

Tōtōsai, much like Myōga, comes off as a cowardly old man. However, this may be because he simply wants to avoid a needless fight. This is shown in a specific manga issue where Sesshōmaru and InuYasha are battling. In order to save InuYasha, Tōtōsai distracts Sesshōmaru by breathing fire at him, right after telling Kagome and the others to get InuYasha to safety (though he manages to escape unscathed as well). He also assists the group many other times, telling them useful information and repairing the Tessaiga and Sango's Hiraikotsu when they break. However, his loyalty lies more with his swords then with the group itself. During one occasion, he strengthens Sesshōmaru's Tenseiga and makes it into a useable (and very powerful) weapon.

His age is currently unknown, although he is estimated to be over 200 years old since he was around before Inuyasha was born, who was around for approximately 200 years, plus the 50 years that Inuyasha was pinned to the tree by Kikyo's arrow, which makes him a very old man.