上(うえ)はOnce, Since, Now that, As long as

上に and 上は share the same kanji but serve different grammatical roles. 上に expresses accumulation of traits or actions, as in 忙しい上に風邪もひいた (I’m busy, and on top of that I caught a cold). 上は introduces a conditional or resolved stance, as in 引き受けた上は最後までやる (Since I accepted it, I’ll see it through).

以上② and 上は both express a conditional premise leading to a natural or expected outcome. Their meanings are very similar and often interchangeable, but 上は feels somewhat old-fashioned, while 以上② is more common in modern usage. Both are relatively formal and typical of written language or structured speech.

上は and からには both present a situation or condition, then express something deemed necessary or natural based on that situation. For example: 日本に来たからには、たくさんの日本人と話したい (Since I came to Japan, I want to speak to many Japanese people). The primary difference is formality: 上は is used almost exclusively in formal writing, while からには is common in both writing and everyday conversation.

以来 and 上は can both be translated as since, but their usage is quite different. 以来 means since in the sense of time, as in 日本に来て以来、毎日日本語を使っている (Since coming to Japan, I use Japanese every day). 上は means since as in because of the given situation, as in 日本に来た上は、たくさんの日本人と話したい (Since I came to Japan, I want to speak to many Japanese people).