A Sister's All You Need

Itsuki falls asleep at the kotatsu and has a dream. He dreams about his darker middle school days. His mother had just died and he falls in love with a certain girl, but... Back in modern time, Itsuki celebrates his book becoming an anime and has a mixer at his apartment. Haruto brings over a board game about being a light novel artist and they all play. What kind of results will they all get in the end?