Twin sister of Junna's friend Tomokazu-kun. She seems to have a serious personality and stoic expressions. She is also the Keeper of Time.

Based on a game by Princess Soft 
The main character, Junna has a twin sister Senna. He is an ordinal student of an elite school. However, in the past, a traffic accident deprived him of his parents and his memory. Junna survived the accident, and he has lived only with his sister though he has been looked after by his relatives. 
And present... 
The life with Senna in the same high school is so pleasant that he can forget the severe past. Because he has been in the world where there is only Senna, his lives in this town, such as the beginning of a new life, new environments, and the meetings, are so refreshing. 
However, he begins to recall the memories he lost in the accident. Though he enjoys happy and pleasant days, he is tossed by the past, the present, and the future. What is the truth hidden in his memory? 
(Source: AniDB)

[Blog](http://blog.excite.co.jp/matsukimiyu/)

She was a voice actress affiliated with 81 Produce. Matsuki was a graduate of Hiroshima Jogakuin Junior & Senior High School and Keio University where she majored from the Faculty of Environment and Information Studies. 

Her parents were officially against her becoming a voice actress but permitted her to move to Tokyo and visit the Keio University after she passed an entrance exam for it. After graduating from university she started pursuing her voice acting career and went at the same time to the Nichinare narration school and the Aksent voice acting school, where she later signed under after becoming professional.

She made her debut under her real name, Matsuki Mieko (松木美愛子) in 1988 on Nude Maker's PlayStation game Mikagura Shoujo Tanteidan. But changed shortly after to using a pseudonym instead as to protect her name.

In 2000 she passed an audition and became a member of newly established pop act Up Up under the Akatsuki Project label. In 2002 she got her first major role in an anime tv series, Shichinin no Nana. During the same year, in June, she quit Aksent and signed with talent agency 81 Produce. She became a regular on two radio shows, Sakurai Koubou and Cherry Bell in October 2002. The following years saw her involved with the Da Capo franchise a visual novel, adapted into an anime, where she played one of the main characters, Sagisawa Yoriko.

Matsuki had been under treatment for acute pneumonia since July 2015. She was diagnosed with a malignant lymphoma caused by the chronic active Epstein–Barr virus infection (CAEBV) and passed away on October 27th 2015. A posthumous charity event had its proceeds go to CAEBV research, which, along with the medical history of her rare case, has helped establish the disease's mechanism of infection and possible treatment.

(Source: Wikipedia)

Tomo Kishida