ペテルブルグの５０２基地に厳しい冬の時期が到来する。初めて体験する北国の冬に当初は嬉しそうな様子のひかりだったが、徐々にその過酷さを実感するようになっていく。そんな中、冬を楽しんでもらおうと、サーシャとニパがレクリエーションを企画する。それは凍った川で泳ぐという寒中水泳大会だった…。
A harsh winter season is coming to St. Petersburg's 502 base. Hikari seemed happy at first in the northern winter, which she experienced for the first time, but gradually she began to realize its harshness. Meanwhile, Sasha and Nipa plan recreation so that they can enjoy winter. It was a winter swimming competition to swim in a frozen river ...
