I re-read 5 times the theory part and still don't understand what they mean and why Setsu destroyed it.
It is because they falled apart in group and were reunited by Setsu?
Same here done a few re-reads (I do love oddman 11 heheh) and from what I can gather, Setsu ended up being a more fitting replacement for the Itami brother considering he dated all the oddmen at some point but couldn't fulfil their needs and vice versa. The only thing kind of banding them together was fear of the Itami sister before Setsu showed up. Setsu is reigning harem master considering she naturally earned their love and trust and achieved it all based on mindset, strategy and ability, though apparently not on her own accord but the Itami sister.... All seems like pretty cohesive story so far but it is a Douman Seiman manga so who knows what the outcome will be...