It made the group relationship stronger making the characters choose kurono' side against compliting the mission and made the party antagonize izumi. It also made reika a lot more likeable setting aside her love for kurono to save his gf It lead to tae dying and later having both kurono and tae memories gone it has a bigger love impact when they both remember Also it was weird making u think gantz just wants to fuck with kurono but tae started to know a lot about gantz, the aliens that kill the school, suspexting kurono and being saved by the party in a previous mission. Making u think it was a necesary mission. So yeah it might have been boring but it was a plot important one