Monday Michiru Sipiaguine (maiden name Mariano, more commonly known as Monday Michiru / MONDAY 満ちる born 19 August 1963) is a Japanese American actress, singer, and songwriter whose music encompasses and fuses a wide variety of genres including jazz, dance, pop, and soul. She is arguably best known for being a pioneer of the acid jazz movement in Japan in the early 1990's yet she has created her own unique style of music that transcends traditional definitions of the aforementioned genres.

Monday was born in Tokyo, Japan to jazz pianist Toshiko Akiyoshi and her now divorced husband, jazz saxophonist Charlie Mariano. At an early age, she expressed an interest in music; she studied modern dance and ballet from age eight, and the classical flute for eight years. It wasn't until she went to the Interlochen Arts Academy that she discovered her true passion of singing.

In 1987, Monday appeared as a lead in the movie “Hikaru Onna” (Luminous Woman) in which she was credited as Michiru Akiyoshi. Monday's unintentional acting career took off as she won Best New Actress awards from Kinema Junpo, The Japan Academy, and the Yokohama film festival. With all this success, Monday became somewhat of a celebrity and could be seen on commercial ads and as a “personality” on several major television networks.

In 1991, she re-focused her interests and released her debut solo album “Mangetsu”. Although she continued her solo work, she became a featured singer/songwriter for many other groups and artists including Basement Jaxx ("Always Be There"), Mondo Grosso, DJ Krush, and numerous others.

Since her debut, she has released over twelve albums, many compilations and remix projects, and numerous singles. She is currently working with award-winning internet label ArtistShare on her project “Flow" and has released several albums through ArtistShare.

Monday now lives in New York City with her husband, jazz trumpeter Alex Sipiagin and their son Nikita.

She is known in the music industry for releasing "You Make Me" as it was also released in Konami's beatmania and Dance Dance Revolution. It gained moderate airplay and has been a favorite easy listening song with its smooth jazz house music.