About 11.2k coupons to get him from scratch here in sakura event (140 cp per frag). There is actually very little rng involved when you buy that many food sacks. The cost get very close to 5 coupons per point when you buy over 1000 packs.

He cost 140 cp per fragment at 30% off in treasure of sage. 120 cp per frag at 40% off.

He only cost about 110 cp per frag in fateful choice, but that event does not show up often.