Senran Kagura is a video game series about ninja with big boobs and minimal clothing. It's also been pretty successful internationally, despite a certain amount of condemnation from Western reviewers. It's also had multiple anime and manga adaptations, so I should be clear about what I'm reviewing here:

I watched the 2013 series because I watched and liked 2018's Shinovi Master ep.1. If it's a sequel, I thought, I should start at the beginning.

FIRST HALF OF SERIES: empty and mind-numbing.

SECOND HALF OF SERIES: actually quite good.

The show's problem is that it's a boob-obsessed fanservice show with no nipples. No, seriously. There are people who love that and dislike the nipples in the 2015 OVA, but they're wrong. Sleaze and nipples are funny. This, though, is pointless. You've got panty shots, gratuitous bath scenes and a girl (Katsuragi) who regularly lets her unbuttoned shirt flap open with nothing underneath. You might see spring-loaded boob jiggle even when someone's calmly walking forwards. Some girls appear to have teleporting dimensional portals for object storage in their cleavage. Successful attacks only do clothing damage, whether it's from a sword or a shoal of piranha... and yet the show's also trying to be family friendly. (Up to a point.) The bath scenes have Censored Light Glare and so on. No nipples, ever. There are panty shots except when there aren't, due to anti-gravity skirts. This is amusing with Katsuragi, because it's so absurd. To all intents and purposes, half the time she's walking around topless. She won't even button up her shirt when walking through a blizzard.

They didn't even draw in nipples for the Blu-rays. It's self-censored sleaze, which is like non-violent boxing or dehydrated water. Compare with the 2015 OVA, for instance, which is funny because it's so shamelessly proud of its nipples. Mind you, this doesn't apply to the Blu-ray mini-episodes, which are nuclear-level mega-sleaze and yet nipple-free. Some of these are amusing (e.g. the Ikaruga ones), but others are just uncomfortable (e.g. the molestation). Oh yeah, Katsuragi. She's the show's #1 fanservice girl, but also a serial molester who gropes her classmates against their will.

Anyway, the plot.

FIRST HALF OF SERIES: there are five girls at ninja school who count as about a fifth of a character each. They have personalities and are okay, I suppose, but they can be summed up as "exhibitionist molester", "generic protagonist", "overly serious", "pink and likes bunnies" and "overprotective of Pink-And-Likes-Bunnies". They don't do anything that matters. Occasionally opposing them in fights that mean nothing are five other girls, from an evil ninja school called Serpent Academy.

You'll get bored. Then even more bored.

SECOND HALF OF SERIES: the show develops a purpose and becomes watchable. Ep.8 is a two-year flashback of our five heroes joining Hanzou Academy, which is invaluable in turning them into meaningful characters and should have come earlier in the show. They're still not great after that, but they're okay. We actually get to understand Katsuragi. After that, the plot does something that overturns your assumptions and we get to know the Serpent Academy girls too. They're surprisingly likeable on their home turf, but also far more compelling characters than the heroines. They have passion, pain and personal issues.

It's a good show. Not great, but solid. You can see how the franchise became successful and how this show got a sequel, albeit five years later.

ESTIVAL VERSUS (OVA): doubles the cast size, with more five-girl teams. (This is handled better than you'd think. They're okay. Some of them are amusing.) There's also Topless Boob Scissors-Stone-Paper and a swimming pool stripping battle.

If you must watch this series, I'd consider starting with ep.8. You wouldn't be missing much. What's in ep.7... ah yes, the skirt-eating piranha and snakes that say "yaaaah" to sound threatening. (The show's producers paid a voice actor to do that. I nearly had a spasm.) The best character in the first half is perhaps the overprotective Yagyuu. She's not great, but she's more clearly defined than most. There's little dramatic content, with the worst episodes (e.g. ep.4) just being flat-out worthless. After ep.8, though, the show becomes worth watching. It has themes (e.g. family) and a lot more intensity, despite the camp that's inherent in the fanservice levels. I'll be continuing with the 2018 sequel series, which at one point here would have seemed like madness.