以来(いらい)Since, Henceforth

Both mark a point after which something changes, but the meaning and outlook are very different. たら最後 expresses a strong, often negative inevitability, meaning “once (A) happens, that’s it,” and implies that things will go badly or cannot be undone, as in 一度言ったら最後、もう取り消せない (‘Once you say it, that’s it, you can’t take it back.’). By contrast, 以来 is a neutral, factual expression meaning “since,” used to state that a situation has continued from a certain point in the past without emotional judgment, as in 日本に来て以来、日本語を勉強している (‘I’ve been studying Japanese since I came to Japan.’).

以来 and 以上② can both be translated as since, but function differently. 以来 marks a continuous state from a past point, as in 事故以来、運転していない (I haven’t driven since the accident). 以上② expresses conditional logic or justification, as in 勝負する以上、全力でやってみたい (Since I’m going to compete, I want to give it my all).

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).