Ranmaru is one of the generals serving under Oda Nobunaga. When most retainers deserted the Oda House in its decline, Ranmaru was among the few loyal ones remaining.
She likes Shibata Katsuie.
Appears in: Sengoku Rance
See wikipedia:Mori Ranmaru / wikipedia:ja:森蘭丸 (Male) for the historical character reference. Note that the kanji for Ranmaru is actually different (乱丸 instead of 蘭丸).