NiksElDrago
Well, for animal, we've been saying spider for a while now. Fits her affinity to using threads and genjutsu and her general shadyness as a shinobi. Also, it looks cool, and it's not been used by anyone before, so you're pretty free on what they're like.
not an animal but maybe something like spirits or yokai. because she reincarnated, the connection with genjutsu and the whole yin and yang thing, I think she would have a strong connection with the otherworldly. the nue was apparently a thing in boruto so it could work. maybe the boss is the reaper and it knows something about her reincarnation?
Spiders 100% Thread combat, poisons, stealthy... Honestly sounds like a match made in heaven as far as summons go. Spiders also have quite varied subspecies abilities irl like irritating hairs, jumping power, many MANY venom varieties... The bigger haired ones would even function like senbons they could coat in venom or poison before flicking them.
Butterflies: The small size will help with espionage and murder. They have a great sense of smell and direction(search Monarch Butterflies migration). They can form clouds of butterflies for distraction and are usually related to beauty and illusion(Yin release). They can feed on blood and even excrement so they can be used to clean up crime scenes. Their wings are made of scales that fall like dust when they fly, you can create a summoning that release poisonous scales. Some of then have designs and patterns on the wings that confuse predators and sometimes frighten other animals (there's a butterfly with owl eyes patterns in the wings). Their larvae can generate silk so the summons can generate silk infused with chakra. They have a perfect 360° visions. Their mouth are a tub like organ, you can create a summon that use these tubs to ingect venom or drink blood.
Well if you want one different from the big 3 . Bear wolf (honey😏)badger dolphin/whale moose/deer/horse tiger/lion/panther bull/cow eagle/hawk rabbit(could have leg taijutsu with soru/geppo/rankyaku combine Tsunade super strength with that and let all fear Sakura) turtle(could become jinchuriki for 3tails later) crocodile/alligator Personally I hope she becomes a deadly bunny or cow cus the sage mode with those would be awesome
big pink butterfly, it has the ability to fly and broke into small butterflies with sharp wings, high speed movement perfect for offense and defense just like captain Byakura from BLEACH that ability was cool flying summon is very special in naruto beacause majority summon in OG naruto is on land:snail, frog, snake,not cool at all. It also represents beauty and being reborn as new like what others have said.. . WELL I THINK AUTHOR HAS ITS OWN PLAN FOR IT TTHIS IS JUST MY SUGGESTION
butterfly summon - genjutsu - camouflage (perhaps light camouflage?) - 360 sight (sakura may be able to connect to them all) - butterfly wing? (perhaps some secret jutsu of the summon to allow contracters to bear wings?) - coccoon jutsu? ( sth like rebirth or escape type jutsu? or maybe used defensively?) - catterpillar (silk), hmm i dont know what will be the silk for but author surely will have an idea, wont he? - catterpillar eats and develop into coccoon and butterfly, perhaps catterpillar eats certain chakra to gain certain affinity and some resistances? wouldn't it be nice to have?
I agree that spiders seems to fit her very well, but I also want to point out rats who have quite a lot of overlap. There is a rat summons Yamanaka story on fanfiction years back that was really good. The idea was that the summons were what she needed and not entirely how she was. The rats were Spies, Thieves, Rogues, Assassins, Saboteurs, Guerilla war fighters, Masters of plagues, poisons and blades. They were honestly the most ninja like summons I've ever seen in fanfiction and I think they would make a good summons for anyone willing to fight their way tooth and nail towards the top. I honestly don't see much diffrence with spiders other than that spiders don't have as much of a physical and verocious presence due to their normal sizes. Another animal that may work are badgers or wolverines. They're cousins with the former less aggressive and the latter so aggressive it willingly fights off its grizzly bear cousins. More claws and brute force tough than anything fairly useful other than as a combat summons. Likewise, they can't really hold weapons either as their bodies don't fit a 2 legged rendition the way rats do, that could go all master splinter turned creepy boss of the underworld.
Just go whith the bears 🐻(polar,Brown,panda,etc) : it go well for earth and water affinities, strong in fights, the cubs are extremely cute, go well whith her personnality of protecting it s kin, can use it s odorat in tracking missions, Can be surprisingly stealthy, (i want to see a bear-punch😅), it is as cool as it is likeable and merciless fighting. Thanks for the chapter.