Personality
With a rogue’s charm and the sex appeal and drive of 10 men, Ranmaru chases (and usually gets) any woman he desires. It should be noted that he can often be clueless to everyday life, and occasionally is viewed as callous by viewers. Ranmaru, like his fellow roommates, only allows most people at arm’s distance, with only a select few allowed into his innermost thoughts.
Ranmaru seems to consider himself an expert as to what will induce Sunako to become a lady, claiming that a girl needs to be appreciated in order to “shine”. He is usually the one who develops what he believes are appropriate ultimate dating scenarios, which usually involve forcing Kyohei to take Sunako to an expensive restaurant and then to a romantic movie (which usually results in neither occurring as Kyohei finds it too uncomfortable to put himself through with Ranmaru’s plans).
His character has often been compared to historical figures, with many similarities being intentionally included by the author.
History
Ranmaru, like Takenaga, comes from a wealthy family, though his wealth is derived from his family’s chain of hotels. Ranmaru’s parents moved the somewhat unwilling lad into the Landlady’s house since they believed that he needed a dose of reality; his family viewed his womanizing and lack of reality troublesome. Ranmaru’s initial treatment of his roommates was rather rude, but as bonds formed between the boys he eventually learns better ways of treating people.
Ranmaru’s morals have been occasionally debated in the series, since he thinks nothing of sleeping with a married woman. In one story his paternity to a young boy was questioned, with his initial reaction being seen as sleazy. Ranmaru’s ability to adapt (and Sunako’s cold treatment of him) led him to treat the child properly, only to discover that he was not the father.
Oddly enough, Ranmaru is also highly skilled with swordsmanship. Several chapters in the manga indicate that he has never been beaten by neither Takenaga and Kyohei, rising victorious in every occurrence.
Relationships
Ranmaru’s relationships with women are usually purely physical, with his more serious friendships being with men (and Sunako). It could be argued that the character of Ranmaru sees women as objects, not as people. Evidence of this can be seen throughout the series, as very few of his conquests are ever named or given any distinguishing remarks, though there’s a running gag about his relationship with the school nurse.
Later in the manga series he meets his arranged fiancée, Tamao Kikunoi, which he at first viewed as being a burden. After several encounters with the girl, whom he initially tried to dissuade, Ranmaru briefly entertained the idea that he might actually be in love with her. His friends, still thinking Ranmaru wanted to get rid of the girl, called up some of Ranmaru’s ex-girlfriends to drop in on Ranmaru and his fiancée and effectively angered the fiancée for Ranmaru’s womanizing behavoir. Despite this, she still appears to have feelings for Ranmaru, who does not appear to reciprocate them, until the end of volume 19 when he finally confesses to her while on a trip to the woods, which leads to Ranmaru initiating a kiss between himself and Tamao.