ISLC

Download the tool for free and launch it without installation after extraction
https://www.wagnardsoft.com/forums/viewtopic.php?t=1256

Select

Start ISLC minimzed and auto-Start monitoring.

Launch ISLC on user Logon.

for convenience

Hit Start to let it do it works and it will automatically effectively negate the effects of what you know as “memory leak”. Keep the window open while you play Nightingale – minimise only.

The default values are good as they are for Nightingale and any PC setup.

Enjoy!

Thanks to アンジェル for their excellent guide; all credit belongs to their effort. If this guide helps you, please support and rate it here. Enjoy the game.