I found something confusing in Korean Grammar In Use – Beginning – English Version page 228 about V-(으)ㄹ래요. 😅
The book says:
V-(으)ㄹ래요 expresses the fact that the speaker has the will or intention to do something. It is used in colloquial language among intimates, and does not confer a feeling of politeness.
How come V-(으)ㄹ래요 does not give a sense of politeness? The -요 form is polite and used in formal situation. 😕
So I looked it up on “Korean Grammar Dictionary for Foreigners 2 – Usage” (외국인을 위한 한국어 문법2 용법편) which is available online and I found this sentence in the explanation about -을래:
‘요'(1)가 붙어 높임 표현 ‘-을래요’가 된다.
When 요 sticks (to -을래), it becomes polite expression -을래요. ###