Bad! Introducing Sanosuke, Fighter-for-hire is the fourth episode of the Rurouni Kenshin anime series.
Sagara Sanosuke is shown in the prologue beating up a bunch of people with his left hand, while holding the Zanbatō in the other. His victims beg him for mercy and he looks at them in disgust, saying that such weaklings aren't worth his time.
Some time later Himura Kenshin and friends all head towards the Akabeko to eat beef hot-pot. While they are eating, a bunch of ruffians calling themselves "desparadoes for democracy" begin shouting and arguing with one another out loud and during their argument Kenshin senses an object thrown by one of them, flying towards him. Instead of dodging it, however, he sits still and it breaks on the back of his head. Kamiya Kaoru and Myōjin Yahiko are disgusted by their behaviour and Yahiko demands them to apologize for what they did. In response, they start acting more rude and boastful, saying that little children should not get in their way.Sekihara Tae tells them to settle down and one of them punches her in the face, causing her to fly backwards. Sano, who is inside the restaurant catches Tae, preventing her from falling. Sano too is sickened by the thuggish behaviour of this group and openly calls them hypocrites for using the name of democracy, while abusing the weak and innocent. They then challenge him to a fight outside, to which he agrees.
Sano easily pummels the leader of the group with just a flick of his index finger and when one of his allies tries to draw a sword, Kenshin stops him and they back away. Sano then briefly meets with Kenshin, admiring him for purposely being hit rather than moving when a plate was thrown in his direction, as this would cause Kaoru's face to be bloodied. Kenshin denies this however and Sano is impressed by his humility, challenging him to a fight, which Kenshin refuses. Sano then leaves, saying that he can meet him at the "Ruffian row House" whenever he wishes and Yahiko and the others note the "Aku" symbol on the back of his shirt (meaning evil).
Meanwhile, Hiruma Gohei has been lurking in the shadows observing what is going on, hoping to hire Sano, then known as the street fighter Zanza, in order to get rid of Kenshin, and he can be free to wreak havoc upon the Kamiya Dojo. After informing Sano that Kenshin is really Hitokiri Battōsai, the former is pleased and takes up Gohei's offer. As Sano walks away holding the Zanbato, Gohei notes that everyone who has fought him are haunted by the memories day and night and that the money he charges his employers' depends entirely on how entertaining a fight is for him.
Sano reaches the Dojo and Kenshin, sensing his presence, steps outside to see what he wants and Sano tells him that he no longer has a choice regarding this fight, since he is now a client. He tells Kenshin that he knows who he really is and has no greater wish than to defeat the strongest of the Ishin Shishi, namely Battosai. Sano attacks Kenshin several times, but Kenshin easily dodges, however, when Oguni Ayame and Oguni Suzume step outside to see what is happening, Sano ceases fighting and goes away, saying that he never takes part in battles with women and children nearby and then goes away.
Kenshin knows now that this is not a battle he can avoid.