Short form of extra modest expression


I recently came across an example of someone saying 'お返しする' rather than
'お返しします' about 18 seconds into this video:

[https://www.youtube.com/watch?v=vazHI4jN6lc&t=18s](https://www.youtube.com/watch?v=vazHI4jN6lc&t=18s)

Under what circumstances should people use the short form of an extra modest
expression? Or does it have something to do with the fact that the speaker is
a child?




A simple answer is, yes it is used as お返しする since the speaker is a child. It
looks like the girl speaks without です/ます endings, and that is why お返しする is
used.

Probably a confusing thing is that お返し is certainly お＋返し, but to mean _the
favor in return_ , お返し is the only possible form.

You can see many samples mentioned in the definition of
[返し](https://dictionary.goo.ne.jp/word/%E8%BF%94%E3%81%97) are prefixed by お,
and those お cannot be omitted.

In other words, お in お返しする exists because of vocabulary, and not (very much)
of 敬語. I cannot really think of other phrases (usable by a child) to mean
_return the favor_ than お返しする. (Maybe お礼する is possible, but again お cannot be
omitted)




A simple answer is, yes it is used as お返しする since the speaker is a child. It
looks like the girl speaks without です/ます endings, and that is why お返しする is
used.

Probably a confusing thing is that お返し is certainly お＋返し, but to mean _the
favor in return_ , お返し is the only possible form.

You can see many samples mentioned in the definition of
[返し](https://dictionary.goo.ne.jp/word/%E8%BF%94%E3%81%97) are prefixed by お,
and those お cannot be omitted.

In other words, お in お返しする exists because of vocabulary, and not (very much)
of 敬語. I cannot really think of other phrases (usable by a child) to mean
_return the favor_ than お返しする. (Maybe お礼する is possible, but again お cannot be
omitted)

