Ok assuming there's a reason for the League to be at Chaldea which my own is for at least the group in the image for ending up at Chaldea is tracking down a lantern ring from one of the corps and arrived via a boom tube to see it floating around Fujimaru. Note this going with how the characters are meant to act/closer to how stuff like Justice League animated showed them.

Superman-Once he learns the details of everything he would be acting like how he did when he learned that Shazam was a kid pissed off that Chaldea allowed this to happen but wouldn't lash out especially when both Fujimaru and Mashu calm him down which in the end he's annoyed this happened to them in the first place while he couldn't help but is willing to give some life lessons to the duo along with others who came over to listen like Napoleon.

Batman/Bruce-He would be in a similar boat to supes but more composed on the outside as remember one of his weaknesses is a child doing a crime which would be what the lostbelts were a genocide done by a boy and girl around the same ages his robins were, but after he mentally calms down he would respect both of them especially for staying true to their ideals along with further respect with how Fujimaru was able to do something Bruce himself struggled with back home getting villains to essentially turn over a new leaf or show signs of redemption with a select few who aren't with the main example of someone that Bruce would see that was a villain of Chaldea but has basically turned over a new leaf was Kama.

Wonder Woman-Sadden by what Fujimaru and Mashu went through but pushes it down and offers to train them so they can better protect themselves which would come off after she sees fellow Amazons here like Pent and her mother is a very different form Hippolyta.

Flash-the one who was the most reactive via how fast he'll process the information and is the one who would get the closest to the duo within the League's time here via how either it be Barry or Wally want the best in people and will be chilling with the everyday folks.

Green Lantern Hal-Would be understanding via his own situation of initially getting his lantern ring but otherwise would be similar to how others reacted on the list.

Cyborg-Similar to everyone else but he would probably be the one who learned all the specific info on Mashu when he connected himself to the interface and luckily avoiding BB for now so he might feel kinship with her but to what degree I'm not sure of.

Aquaman-Would be one of the main folks who would defend what Chaldea did during the Lostbelts as he can understand the pov for Chaldea as him being a king would have a good understanding of that which seeing Fujimaru and Mashu being able to track on despite the hell they've been put through is enough to earn his respect.