The protagonist, Kaburagi Jin, and the heroine, Asamiya Mika, are engaged.

On a day near the end of winter, the two set out on a 3-day, 2-night snowboarding trip with their close friends, Sawamura Tokushi and Ichijou Aoi.
However, a sudden blizzard hits, and Mika and Tokushi go missing.

"Please be safe…"
Jin and Aoi spend a sleepless night filled with worry, but the next day, the weather clears, and the two are rescued safely.

After that, life returns to normal, and peaceful days continue. But as time passes, Mika starts acting strangely.
Then, one day, just before their June wedding, Mika drops a bombshell.

"I’m pregnant… with Sawamura’s child."

And so, the days of despair begin—

[Translated from dlsite]