Koshiro and Aria Only Act Affectionate in Russian

Because none of their classmates know that the two of them are dating. ※This is a follow-up story and conclusion to the short stories "The Girl Next Door, Arya, Who Occasionally Gets Shy and Speaks Russian" and "The Boy Next Door, Himuro, Who Doesn't Notice at All Even Though She's Getting Shy in Russian." You won't understand the content unless you read the previous works first.