Days with My Stepsister, Vol. 5 (Manga): Volume 5

Now aware of their feelings, Yuuta and Saki are still unsure of whether the affection they feel for one another is familial or romantic. To find out, they decide to try deepening their relationship, unbeknownst to their family and friends. As they go on their first date for Halloween, will those secret, uncertain emotions develop into something more...?