"Gintama" manga volumes 65 and 66 will bundle OVAs adapting the Love Potion arc.

Yoshiwara is besieged by a mysterious incense that has the ability to make whoever smell it fall for the first person they see; poor Tsukuyo is hit, her already secret attraction with Gintoki intensified. In trying to gather the incense, Tsukuyo's slip-up causes the entire district to be affected by the smoke, including the Yorozuya (and Tae, Kyuubei, and Kondou who happened to be there at the time). Can the Yorozuya and Tsukuyo overcome their afflictions to stop the perpetrator?

(Source: Gintama wikia)