Izou loved his sword as if it was a living being and would even talk to it. He claimed that Kousetsu needed to be fed blood regularly - something that the sword itself apparently told him, along with its desire to drink rare blood, such as of a Night Raid member. He also mentioned that it outclassed Murasame in terms of "brilliance". When Izou was cut down by Akame, he asked her to take Kousetsu in order to continue feeding it, however, Akame refused the offer. Kousetsu is not a Teigu or a Shingu, and it does not require blood. According to the Akame ga Kill! Official Guidebook, Izou is just delusional, thinking that he must feed Kousetsu.
- Kousetsu's name is written with the kanji for "large river" and "snow". When written as 降雪, it can mean "snowfall", and when written as 紅雪, it can be translated as "red snow".
- Kousetsu's concept is loosely based around the famous Japanese swordsmith Muramasa, which tells of a cursed blade that has to draw blood before it can be returned to its scabbard.