[合「あ」]う => To do A together/mutually N4
Secondary Verb
に[対「たい」]して/に[対「たい」]しては => In response to (topic) A, in regards to A, considering A, in contrast to A N3
Reason, Result, Response
に[対「たい」]して/に[対「たい」]しては => In response to (topic) A, in regards to A, considering A, in contrast to A N2
Reason, Result, Response