It's too early to ask advice, the harem has little to do with Ichiro's ability to make it, it was the circumstance and Kurumi's unique mindset to help out Ichiro. Kazumi, Kurumi and later Ayase also have good friendship, that's one less friction to worry about, and helps lessen Ichiro's social burden to maintain relationship (but you wouldn't make your partners feel they're not getting enough of love, in couple each other would receive full love, but having multiple partners, you can only give so much love before being exhausted, so partners may receive less than standard couple would receive and become unsatisfied with the situation). And it's only been few months, they're still in honeymoon phase, who knows whether the relationship will last.