City: Swap Bodies with the Senior Sister at the Beginning

My name is Yamashiro Ichi, an ordinary high school student. Today is December 24th. The day before Jesus Christ was born. It is a day when lovers go on sweet dates, relatives and friends meet for dinner, and children look forward to receiving gifts. It's a day of excitement and planning for love and desire. This is how it should be. This is how it should be... But the sudden arrival of aliens disrupted everything. I actually swapped bodies with my favorite senior? ? ? ! This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.