Sensual Phrase

Everything About Fiction You Never Wanted to Know.
Play misty for her, baby.

Aine Yukimura is an Ordinary High School Student with rather low self-esteem, who is good only in one subject at school: Japanese. Her dream is to become a song writer, and as practice she writes some very raunchy lyrics for a song and goes to the post office to send them for a contest.

On the way there, Aine is almost run over by a car. The driver is Sakuya Ookuchi, lead singer from a band named Λucifer that is known for its sexy music (Aine herself isn't exactly a fan, but she knows how famous they are). He grabs a hold of the lyric sheets and takes them with him... and, after singing the song on-stage in front of a bewildered and confused Aine, manages to convince the girl to become the songwriter for the group. Aine reluctantly accepts, unaware that her life will take a turn for either the worse or the best, as she and Sakuya become involved in a very tormented and complicated relationship: not only the poor girl is completely unprepared for the bitterness of fame, but Sakuya turns out to be extremely screwed up...

According to The Other Wiki, Sensual Phrase (快感♥フレーズ; Kaikan Furēzu) is a shōjo manga series created by Mayu Shinjo. The manga was published by Shogakukan in Shōjo Comic between 1997 and 2000, and collected in 18 bound volumes. It was adapted as a 44-episode anime television series by Studio Hibari, a CD drama, and as a series of novels.

To promote the anime, two real-life bands were formed: Λucifer, the band the story focuses on, and e.MU, a rival band. Both bands continued after the anime ended before disbanding. Within the series, Λucifer’s original name is Lucifer, which is changed to Λucifer (using the Greek letter lambda) when the band decides to go international.

Tropes used in Sensual Phrase include:

Atsuro (to Riri): "If you want to make my relationship with my older sister public, then do it. But if it hurts her feelings... If so, I will personally make sure your life is a living hell. For my sister, I can even be a devil."