Jyukai (樹海, Jyukai) was formed in 2004 and is sometimes referred as Jukai.
Dewa grew up learning to play piano and his older brother recruited him to a cover band where Dewa grew to be a creative force, but after three years the band disbanded. He decided to search for a vocalist he could recruit to his group and realise his vision of how music should be: eternal, heart-touching and soulful.
There's a popular but unverified story about how Manami and Dewa decided to start a band together:-
During his search he attended a karaoke session with friends. It was there when friend Manami's singing impressed him enough to recruit her.
Jyukai roughly translates to 'tree sea' (forest), which is commonly referring to a forest at base of Mount Fuji and the forest is locally known as 'Suicide Forest' because it's a popular spot for those who choose to end their lives. But Dewa strongly believes Jyukai is a place of birth, spiritual force and purity where one can create songs that touch hearts.
Jyukai has written several songs for various anime series including:
'Hikari' (ヒカリ) and 'Anata ga Ita Mori' (あなたがいた森 ) for 'Fate/Stay Night'(フェイト/ステイナイト )
'Hoshi Akari' for anime series 'Busou Renkin'(武装錬金)
'Koibito Doshi' for 'Ah! My Goddess: Everyone Has Wings'(ああっ女神さまっ それぞれの翼)
These contributions won them a small but strong cult following.