Brigadoon: Marin & Melan (2000)
Original title: BRIGADOON まりんとメラン
Brigadoon: Marin & Melan is a 2000 Japanese-language action & adventure series. It stars Ayaka Saito, Hikaru Midorikawa and Yuji Takada.
When the planet Brigadoon appears in the sky, Marin is attacked by weird mecha called Monomakia. In an old shrine, she finds an ampoule that contains Melan, an angular blue mecha who swears to defend her.