Minamitsu's first name (水蜜) means 'Water Honey'. Murasa (村紗) is a name of Funayuurei, which can be found in folklore of Shimane Prefecture. Funayuurei are the vengeful spirits of people who have died in sea.
Her stage theme has a distinctive Windows XP balloon hint "pop" around 2:10, which probably got in the recording, as stated in ZUN's Twitter.
Like Aya Shameimaru in Mountain of Faith, Minamitsu Murasa doesn't seem to have a gimmick/variation based on the playable character (which is something usual in stage 4 bosses).
In addition to that, like Aya, she has a survival spell card (and she doesn't have it on Easy mode).
Her name is similar to that of Minamoto no Yorimasa (The archer who supposedly sealed Nue Houjuu).
In some fan fictions, she is fond of Japanese curry, because curry is said to have been eaten first and introduced into Japan by members of the Imperial Japanese Navy. Even the present-day Maritime Self-Defense Force has it for lunch every Friday in order to remember the day of the week even if they are at sea. (The Japanese Wikipedia even has a page about it: "海軍カレー".)
She has been shown wielding her anchor as a weapon, and this has been the source of parody images comparing Murasa to May from the Guilty Gear series.
Strangely, "Murasa" is written in kanji in UFO's manual, but is written with katakana when she appears in the game itself. This is not the case with Double Spoiler, though, where her name is flashed in kanji.
Minamitsu is one of the three characters that owns a boat, along with Komachi and Futo, although her boat is more like a ship.