Ep. 4: Koyomi receives the demon sword Heartspan to defeat the Oddity possessing Tsubasa.

After days of pleading, Shinobu gives Koyomi the demon sword Heartspan, which kills Oddities without harming hosts. Koyomi tricks Tsubasa into visiting Oshino by feigning a vampire attack, then criticizes her possession, causing her to attack him. She slices his body in half, revealing his plan to have her cut by the sword hidden within him. Tsubasa refuses to release the Cursed Cat, so Shinobu restores Koyomi and cures Tsubasa. The next day, Tsubasa returns to normal with no memory of the incident. Oshino suggests Koyomi marry her to provide a family, but he declines, stating he cannot love her despite caring for her. Later, Koyomi prepares to meet Hitagi for the first time, setting the stage for Bakemonogatari.

▶ Watch on Crunchyroll