Isshou Hitori de Ikiteiku to Kimetanoni Chi no Tsunagaranai Ani ga Doukyo Shite Kite Komattemasu

30-year-old Seri is inherently unlucky, so much so that her intended husband was arrested for marriage fraud. When she returns home, she finds her mother has married for the fourth time and suddenly has a new father and a brother two years older than her. Seri flees to her grandmother's house, but her grandmother is away on a trip. One day, she returns to her grandmother's house to find her step-brother, Tatsuma, and the two of them end up living together...!?

(Source: Shogakukan, translated)