two
弍 is a rare variant form for the number two, essentially a different way of writing 二 with an added 弋 component.
弍 is a variant form of 二 (two) with the addition of 弋, likely created as a formal or alternative numeral to prevent forgery, similar to how 壱, 弐, 参 are used for one, two, three in legal documents. The exact historical development is uncertain.
The number two 二 is enclosed by 弋, like a special seal or stamp marking it as an official, formal version of two.
For ニ, picture a knee (ニ) with a stamp 弋 on it, marking it as the second knee: knee -> ニ, and the stamp makes it the formal two.