@Phrog1005 Well, Renka won't do anything until the beach trip, she has made that known. She's not doing anything without Irina present and Xenovia isn't going back to Italy, Griselda is having her go to England and Issei will be visiting Irina again, which is before the beach trip. Don't forget, Xenovia was present when most girls spoke with Irina about their interests. Don't doubt the cunning ability of Xenovia because she has intel. This isn't power idiot from the canon, she's refined in her swordsmanship thanks to Mitsurugi and that will progress thanks to Siegfried.
Also Irina isn't going to force Issei to go after anyone either, she's selfless by giving the girls a chance. Something that Michael will note upon her ascension to angelhood. However, if Issei says no, she's going to feel conflicted because she would wonder how it would affect friendships, which is actually something Issei takes into perspective and why you will see him talk with guys that have multiple girls that like them, Kenichi is one example and also Tobio.
And another thing to note for why he wouldn't go for Renka first is because he still believes that she likes Kenichi. Remember, Renka was his first crush and she liked someone else in his eyes. It's something Renka facepalms about to this day, if she had stopped with her teasing of Kenichi and Miu's relationship, yeah, she and Issei would have been dating before Irina ever arrived, likely after the tournament.