misanga bracelet; friendship bracelet
A good luck charm made from knotted embroidery floss, thread, or gimp. Often tied around the wrist or ankle and worn until it falls off naturally, at which point a wish is said to come true. The word comes from Portuguese 'miçanga' (bead), but in Japanese it refers specifically to this knotted bracelet.
from Portuguese miçanga
I've been wearing the misanga bracelet I got from my friend all this time.
ミサンガが自然に切れると願いが叶うと言われている。
It's said that when a misanga bracelet breaks naturally, your wish will come true.