See post #3187783.
Upon reaching kai ni, Shiratsuyu's hair is now longer and shifts towards a faint blue color, while sporting the distinctive hair flaps seen among her remodeled sisters. She also wears a whistle around her neck. In addition, her breasts become more noticeably prominent.
Her outfit now includes fingerless gloves and a longer right sleeve, while her legwear changes to thighhighs, giving her zettai ryouiki.
As for her rigging, she replaces her 12.7 cm single gun mount Type A with a second twin mount Type C in an attachment on her left that also includes her historic Type 22 radar. On her mast, the flag signals "5" and "Z" are flown from the halyard.