Thank you @megari for the info and the hints, but I’m not sure how to proceeded.. Isp pin 5 (reset) seems connected to pin 5 of LSF 204, and its pin 10 goes to atmega’s reset pin: programmer pulse low right the isp pin, but ic’s pins remain high (2.89v). So, where could I add the resistors?
I’m pretty sure my cable connection it’s right, I checked the continuity on isp connection, and my programmers work fine with all my uno and mega arduino boards, so I’m afraid my koryuu has something wrong. I ordered a couple of.atmega328p, but i’d leave the ic replacement as last chance.
UPDATE: i desoldered Atmega328P pin 29 (Reset) and… Koryuu still works fine, so the reset pin was disabled by factory (or, i think, the Koryuu had to stay always in reset state and never start)