|Quotes | Relationships|
|Code Name||Silver Cocoon|
|Relatives|| Koyori (Twin Sister)|
|Hand Shaker|| Koyori (former)|
|Special Skills||Hand Shaker|
Mayumi Akutagawa (芥川万優未 Akutagawa Mayumi?) is the former hand shaker partner and the older twin sister of Koyori and the current partner of Nagaoka. She is known as 'Silver Cocoon' and together they are known as Team Cocoon. She is also shown to be mute like her twin sister.
Mayumi visually has the same appearance as Koyori due to them being twin sisters. She is very cute and has silver eyes and hair. Her skin tone is shown to be very pale. She wears a traditional japanese kimono at all times and has a bundle of flowers sitting on her hair.
Like Koyori she is very quiet and normally does what Nagaoka wants to do. Although before, she was very protective over her sister and was normally the one who put the strong front on and protected Koyori although at times she would cry and run for Nagaoka and Makihara's help along with Koyori.