User blog comment:Piyush Banerjee/Shin DxD 2 discussion/@comment-92.21.29.42-20190623153730/@comment-34061653-20190628145923

Before Issei thought about Nyuutron Beam canon he aleady notice how Rias was vulnerable and considered attacking her before her form recontructed. Again, her countermeasures was just a form of survivability. She didn't have anything that would help her to win. The best way to deal with Issei is to exploit his weaknesses or use means he wouldn't expect. This is why Cao Cao and Sona's countermeasures were successful in actually beating Issei. That's why Dulio's countermeasure to use Gabriel was successful in trapping Issei. Coming up with a way to defend againat his perverted techniques is something Issei has already delt with multiple times which is why Rias failed. Just like her tactics against his team failed because trying to fight Issei head on usually leads to defeat.