A Reluctant Princess
Returning Memories: Usagi and Mamoru's Past
Yomigaeru kioku! Usagi to Mamoru no kako
"Tuxedo Mask is fatally wounded while protecting Sailor Moon. Responding to Sailor Moon's tears, the seven Rainbow Crystals gather to form the Legendary Silver Crystal, and she is transformed into Serenity, the Moon Princess that everyone has been seeking." (source)