とりあえず、転入生は自動的に身辺調査をすることにしているんだけどね
This is taken from a visual novel
It translates to "So anyway I decided to to do a background check on the transfer student"
However I don't get the usage of は in this case.
Using は would mean that the preceding word (transfer student) is the subject and he/she is doing something.
However the something (investigation) is being done to the transfer student so shouldn't the を particle be used here instead of は ?
は does not mark the subject of a verb. It marks the topic of the sentence. The subject in this case is an implied 'I'.
The (indirect) object is indeed 'transfer student' but this is also implied. We don't need to make it explicit because they are already the topic of conversation.
As for transfer students I make it a rule to automatically do background checks on them.
Please check other questions on this site on the difference between は and が e.g. this.
