The conjunction 加上
We use the conjunction 加上 
to add some thought to what is being said.
It can be stated at the beginning of a sentence or connect two parts of a compound sentence.
We usually use the adverb 再 before 加上.
to add some thought to what is being said.
It can be stated at the beginning of a sentence or connect two parts of a compound sentence.
We usually use the adverb 再 before 加上.Scheme
idea 1
加上
idea 2
Examples
再加上这也很简单
In addition, it's easy
zài jiāshàng zhè yě hěn jiǎndān
天气不太好，加上你还有很多作业，我们还是别去吧
The weather is not good. Plus you have a lot of homework, so we better not go
tiānqì bú tài hǎo, jiāshàng nǐ hái yǒu hěn duō zuòyè, wǒmen háishì bié qù ba
加上日本几乎没有移民
Plus there are almost no immigrants in Japan
jiāshàng rìběn jīhū méi yǒu yímín