some noticable things early on that could help you out.

neji is actually a very good ninja if you can 2star him(lvl 40 elite missions should be able to give you free frags on first clears for some of them but your not there yet). he also needs to be in a more forward position either position 1 or position 2 on the team since his mystery is mainly used as an interupt t1 and if you have him position 3 he will not be able to interrupt a ninja in position 1 or position 2. his dodge that he has at 2star is boosted turn 1 meaning if you keep him in the back lines he wont stop much. as a temp replacment front row hinata 2star could kinda help divert damage as well with her mystery allowing her to "dodge" many of the early attacks thrown toward her and has acupuncture on her chase.

guy is also a great ninja for early fights since you get a bit of life steal, an attack boost and an interrupt all in 1 ninja that also leaves 20 chakra for another ninja turn 2. the bonus atk from him can let you to fight at slightly above your power for a bit.

as for water main shark bomb+the chaos on crit passive in row 2(neurotoxin i think) makes for an excellent early mystery since you can chaos multiple characters and have them fight each other rather then you. chaos also interrupts mysteries as well if they are preparing to cast it.

as for the last ninja sakura would give healing,sasuke would bring more damage(and if 3starred brings a barrier that powers up lightning characters like guy and hinata), or naruto brings some clones to soak a few hits.

if your unable to beat it even after a few changes all thats left to do is just try to level up and power up some more to do it again later. daily stuff resets at 5am server time allowing for you to do them all again.

1, take a break from plots, 3* your ninjas, gain more power.

Do this and you'll have no issues.