Thanks for the chapter!
Wonder if Sitri considers MC a worthy partner or just wants to have a chance at facing Phoenix again. LN describes it better but basically low level or mob type monsters like the werewolves can appear on any floor with permission from the floor master. However, Floor Bosses or mid-boss level monsters with a level high enough to be near in power can only appear on their floor and one other floor. Usually on the floor or floor before the Demon Lord or final boss and even then only one or two monsters of that level can show. Only exception is summoning. So by becoming one of the MC's 72 summons they can get another chance at fighting Phoenix's party when they appear on MC's floor. After all, summons can only be done if summoner has enough magic power so the typical human might have trouble just summoning a mid-boss class monster.
Not sure what race the dark skinned girl is but that's the knight Furcus when not wearing her armor. Seems will do anything if paid with a meal. Manga left it out but LN mentions how she kept telling food over and over to MC before he realized she was telling him what she wanted in return for her help. Explanation on why Cashew wanted him to quit making contracts at 71 demons is missing a few key points but basically she was telling MC she wanted him to save the 72nd spot for her once she's old enough to contract with him. This will probably be at least 2 years when she becomes 10 and gets a class, but could be longer along with having no idea what role or abilities she'd be able to provide for him once able to form a contract with him. She could be anything from a mage, fighter, maid or secretary and won't know until she's ten.
@Ashurali Cashew is still young so she'll grow out of being a loli in a few years.