There is another option to consider.
We could straight up use a diplomatic option on the girls in Itawa. It's not a high percentage chance rate, and it doesn't help with the grief cube harvest. So I don't think we should do it, but it is an option.
Okay, rough plan below. After thinking about it I decided to just scout everywhere we can, since we only need a few more grief cubes added to our safe harvest level to make it work out. I decided it was better to maximize our options in case we don't get Kyouko to join us. That means putting off the courier expansion for a month.
EDIT: Updated to use notgreat's idea of under hunting this month with a large over hunt next month.
[X] Upkeep (9 Vets, and 4 Greens)
[X] Mami holds a meeting at the start of the month to discuss the Grief Cube levels. Remind people that we were in this situation before and we made it all work out. Use graphs and charts to show the safe harvest level and our grief cube usage, as well as Demon Strength trends. Identify the water contamination as what has made our safe harvest levels drop. Explain that we will need to expand to be able to return to a safe harvest level. We will be sending out scouts to all the available areas around use this month. Mami will be talking to Kyouko to see if we can use her territory. That will tell us our options. Next month we will expand, either here in Mitakihara area, or possibly down in Itawa, even if it means a territory fight. We have sufficient saved grief cubes to support us with safe hunting levels for the two months it will require to expand. Thank everyone for their hard work and effort, and ask if anyone has questions.
[X] Talk to Kyouko, she'll come around eventually surely.
Cost: Mami; Reward: Variable; Chance of Success: ???
-[X] Ask Kyouko to come to our house for dinner because we want to talk to her about a business proposition. Eat dinner together with Kyouko and some of the girls from your original group that we can get to come to the dinner (should be at least 10, includes Yuma and Sayaka). After dinner shoo the other girls out for a while while we and Kyouko talk.
-[X] Recognize that Kyouko has become strong. Strong enough to survive easily on her own, but does she really want to be alone?
-[X] Point out all the fun things we get to do together. Cultural Festivals and karaoke nights. Cable TV and movie nights. Sports days. Magic research and eating together.
-[X] Mami has prepared graphs and charts (we can reuse some from the meeting earlier this month) on different hunting tactics, hunting casualty rates, Demon Strength, Safe Harvest rates for Mami's and Kyouko's territory, Income and expenses, etc. Demonstrate that with the addition of Kyouko's territory hunting can be done at a safe level for everyone, including Kyouko, while also freeing up enough girls to provide a stable living quarters and some luxuries.
-[X] If Kyouko still doesn't want to join us, propose a share cropping scheme. We can harvest 6 grief cubes from Kyouko's territory, and we give her 2 of them. She gets two grief cubes without having to do any fighting to get them. That's even safer for Kyouko then the way it is now. Suggest we try it next month and see how it goes.
[X] Repeat Basic General Combat Training: We have a lot of new members again. Give them the same training our older members had (and maybe give a refresher course for our older members)
Cost: 1.5 Veterans + .5 greens; Reward: -2% casualty rate on all Hunting actions (From -1%)
[X] Repeat training in defending each other: This many new members means a lot of them didn't go through the previous training. Maybe you should fix that.
Cost: 1.5 Veterans + .5 greens; Reward: -2% casualty rate on pair hunting (From -1%), -1% casualty rate on pack hunting.
15 Vets and 5 Greens left to assign.
[X] Pack Hunting: Magical Girls will hunt in groups vastly reducing the danger, but because they are not covering as much area their efficiency is reduced. Death is significantly less likely.
Cost: Variable, specify number of Meguca dedicated; Reward 1.25 Grief Cubes per Meguca assigned; 10% base casualty chance. 2 Greens, expected grief cubes = 2
-[X] Rural: Base modified to .9, dispatch bonus does not apply.
[X] Hunting Pairs: Magical Girls will hunt in pairs reducing the danger, but because they are not covering as much area their efficiency is reduced. Death is less likely. 8 Vets, 2 Greens = 34 expected grief cubes
Cost: Variable, specify number of Meguca dedicated; Reward 1.6 Grief Cubes per Meguca assigned; 16% base casualty chance
Total expected Grief Cube Harvest = 36
[X] Demon Forecasting: It occurred to you that while the patterns seem random enough that you couldn't predict where demons would appear, that doesn't mean there aren't underlying patterns like the weather. Maybe someone with some more resources could make sense of them. Kyuubey admits that it is possible, but with only your girls' rather imprecise data results will be equally imprecise. Especially given just how many variables effect demon spawn rates due to their connection to human migratory patterns. He'd also charge you for use of the processing time.
Cost: 1 grief cube per turn; Reward: Additional 1.1x multiplier on grief cube gather rate. (Multiplicative rather than additive with others.)
Expected Net Grief Cubes = 38
[X] Telepathic Coordination: Communication during combat could be better. Telepathy is rarely used in favor of yelling, since it's difficult to maintain telepathy in combat. Perhaps some practice with it will help though. As most girls struggle to communicate with telepathy to more than one at a time even outside of combat this will be most useful between two girls.
Cost: 3 veterans + 1 green, 1 veteran upkeep; Reward: -2% paired casualties, -1% pack hunting casualties
[X] Scout Area 1: You can deploy a veteran to scout out one of the territories around you stealthily. They should be able to gauge the demon strength there and the magical girls status there without tipping them off, hopefully.
Cost: 1 Veteran; Chance of success: 70%; Reward: information on demon strength, support capacity of the territory, and status of current magical girls in the territory, bonus to diplomatic efforts.
-[X] Send a different girl this time (Was a -30% to scouting, with decay and new girl this is?)
[X] Scout Area 2: You can deploy a veteran to scout out one of the territories around you stealthily. They should be able to gauge the demon strength there and the magical girls status there without tipping them off, hopefully.
Cost: 1 Veteran; Chance of success: 70%; Reward: information on demon strength, support capacity of the territory, and status of current magical girls in the territory, bonus to diplomatic efforts.
-[X] Send a different girl this time (Was a -10% to scouting, with decay and new girl this is?)
[X] Scout Area 9: You can deploy a veteran to scout out one of the territories around you stealthily. They should be able to gauge the demon strength there and the magical girls status there without tipping them off, hopefully.
Cost: 1 Veteran; Chance of success: 70%; Reward: information on demon strength, support capacity of the territory, and status of current magical girls in the territory, bonus to diplomatic efforts.
[X] Scout Area 4: You can deploy a veteran to scout out one of the territories around you stealthily. They should be able to gauge the demon strength there and the magical girls status there without tipping them off, hopefully.
Cost: 1 Veteran; Chance of success: 70%; Reward: information on demon strength, support capacity of the territory, and status of current magical girls in the territory, bonus to diplomatic efforts.
[X] Scout Area 7: You can deploy a veteran to scout out one of the territories around you stealthily. They should be able to gauge the demon strength there and the magical girls status there without tipping them off, hopefully.
Cost: 1 Veteran; Chance of success: 70%; Reward: information on demon strength, support capacity of the territory, and status of current magical girls in the territory, bonus to diplomatic efforts.
Note: Kaori is one of the Vets assigned to scout the new areas.
[X] Ask Kaori to let us know right away if anything changes in the situation down in Iwata, or if any of the other girls there give her trouble.
-[X] Quietly talk to our teleporters and arrange to have them ready teleport down to Kaori with extra grief cubes in case something bad happens (attacked by other girls, grief spiral, etc).
EDIT: Looking at notgreat's plan, that is certainly another way to go. I'd be willing to consider it with the fluff text I added included. Would like to know what other people's thoughts are and what notgreat thinks about my plan before deciding.