User blog comment:DeathGodPrayer/Talk About What You Want!/@comment-82.40.154.8-20140102232430/@comment-16281343-20140102233350

You basically answered how Euclid managed to replicate Boosted Gear. They observed and collected data from Issei when he was busy foiling the plans and actions of KB.

The reason Irina moved to another place is because of his father's work and their religion.