These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Would it be a stretch to say that Miroku is more desperate than lecherous? After all, if he doesn't have an heir before the Wind Tunnel consumes him, well...
The old lady from the Demon's head arc, is she really a fraud or is it merely Obfuscating Stupidity and she is actually more powerful than she seems, especially since she's not unnerved by the demonic aura that keeps everyone in the main group on the edge,
Arc Fatigue: Most agree that the series was much longer than it needed to be especially the nigh-invincible Villain Sue Naraku and the Kagome/Inuyasha/Kikyou love triangle. Naraku had ridiculous Joker Immunity until the last act. The love triangle dominates so much of the story and is resolved so late into the extremely long-running series that many fans were heartily sick of it, especially given how obvious it was that the outcome was a foregone conclusion. The story was also dragged out by Inuyasha's group being full of Chronic Hero Syndrome, helping anyone in spite of Inuyasha noting this draws them away from finding Naraku and thus the main plot. The Final Arc reverses this issue, cramming more than 20 volumes into 26 episodes, at the sacrifice of one chapter involving a regenerating tree hermit demon never being adapted in favor of Kanna's character development.
Kikyou and Kagome, either good foils to Inuyasha or incredibly bad influences on his behavior. Kagome being extremely clingy and getting jealous for any reason, even if it's not justified and Kikyo, who constantly avoids him and/or manipulates him into getting what she wants. Both their problems (going back to the present to graduate and finishing off Naraku when she's not capable) respectively have dragged down Inuyasha on more than one occassion.
Complete Monster: Naraku is responsible for nearly every atrocity in the series. He is a half demon who wishes to become a full demon by using the sacred Shikon Jewel. How does he want to go about doing this? By messing up the lives of almost every single one of the main cast's lives because he can. He was responsible for Miroku's Wind Tunnel curse, Sango's brother becoming Brainwashed and Crazy, reviving a group of serial killers to slaughter his enemies, and sending his minions to kill villagers to lure the protagonists to him. He's a mastermind at manipulating others to do his bidding and he's killed Kikyo numerous times because he wants to remove the only side of him that could possibly be redeemable. If that wasn't bad enough, he essentially was responsible for Kikyo and Inuyasha's falling out and killed a huge margin of Koga's wolf clan. He's also not above killing his minions if they choose to disobey him and killing innocents if they even so much as become inconvenient to him. A rather despicable act was 15 years, when he tried to kill a young priestess in training named Hitomiko, when that failed, he killed all of her friends and then her parental guardian. And unlike most of his murders, it wasn't to further his plans, it was kill someone on the small possibility that they'd pose a threat; and that's not going into the details when he decides to kill her, resurrect her as a puppet to kill Kagome and then possess her when she wasn't doing the job right.
Sesshomaru. Character Development eventually renders him more sympathetic, but even prior to that he already had a substantial fanbase willing to overlook how in his early appearances he made several attempts at murdering Inuyasha and Kagome over a sword that he honestly didn't even need. In the manga he chops someone's head off just because he was standing there in his introduction.
Naraku. Sesshomaru at least developed in time into a Good Is Not NiceAnti-Hero. Naraku has no such development, and whatever sympathetic traits he might have are overshadowed the fact he tortures, manipulates, and tries to kill every member of the main cast several times over.
Ear Worm: A good deal of the openings and endings.
Many complain that around the third or fourth season the anime begins to drag, pace-wise. This is a complaint of many of Takahashi's work - namely that they're good, but tend to go nowhere fast. However, this doesn't happen as much in the manga, since the aforementioned seasons of the anime are filler-heavy.
Oddly, the second series has the reverse problem. Well over 100 chapters are condensed into a single season of 26 episodes.
Esoteric Happy Ending: Inuyasha and Kagome are hinted to be married and are living content with one another, however the probability that Inuyasha will age much slower than Kagome is never mentioned, meaning he'll most likely still be young looking when Kagome (and Sango and Miroku for that matter) are old. Also, it's never confirmed whether they can still use the well, meaning Kagome could possibly be separated from her family forever.
Yura of The Hair was in TWO EPISODES, and she gained plenty of fanboys thanks to her sexy voice and Stripperific outfit.
Kagura is also pretty attractive for a demoness and gets Clothing Damage to the chest, twice! Although the anime has her breasts covered up during her Clothing Damage, the manga has no problem showing her breasts completely uncovered! Cue nosebleeding fanboys.
Believe it or not, NARAKU himself has plenty of fangirls himself when he isn't shown with Body Horror.
Sesshomaru is the Lord of the West, and he has a manor home or castle somewhere with servants and subjects. In the actual series he's a nomad with no home ever shown, he's not the ruler of any land anyway, though he is a daiyoukai (or at least becomes one by the end of the series), and his only servants are the ones you see with him all the time - and those mostly seem to have latched onto him in spite of his preference. (This seems to have originated with sketchy fan translations, but the notion remains entrenched in the fandom.)
In fact, even Sesshomaru's father never bore any such designation, either. He is only ever called "Inu no Taishou", and while this would translate as "Dog General", in spirit the title could be much more broadly interpreted, which the English version wisely represented with the more ambiguous "Great Dog Demon". He is never explicitly stated as having "ruled" the West, only to have resided there.
If fanfiction ever deals with Kagome growing older, she'll likely become some sort of doctor due to her experience patching up her friends. In Final Act she is seen learning herbalism from Kaede so she'll likely become the village healer.
Inuyasha's addiction to ramen. In the manga, he's seen eating it two times, and mentioning it tastes good. The anime shows his liking of it a little more but nothing remotely close to the “I’ll do anything for ramen” you see in fanfiction.
Inuyasha's tranformation to full youkai being triggered by anger. In canon it’s triggered by fear of dying not anger; the Unstoppable Rage comes afterwards.
In the absence of any Canon Names for them, it's common to see Inuyasha and Sesshoumaru's father referred to in the English-speaking fandom as "Inutaisho" (a corruption or mishearing of "Inu no Taisho" which is then used as a name instead of a title), and Sesshoumaru's mother is popularly called "Inu Kimi" (sometimes "Inu Kami"; the former, though more common, is probably a misspelling of the latter, which is Fangirl Japanese for "Dog God").
Foe Romance Subtext: Kikyou and Naraku. Inuyasha and Jakotsu. Inuyasha and Bankotsu. Inuyasha and Sesshomaru. Inuyasha and Koga.
Freud Was Right: The sword Tessaiga is astonishingly phallic. It even throbs with warmth when "awakened" and grows hair on its hilt. The sword is "awakened" by "protecting" a WOMAN. Plus powerful energies being "released" from it.
Gary Stu / Villain Sue: Sesshomaru, InuYasha's big brother, who hurts whoever he wants to reach his goal. Early in the series he steals his brother's sword and masters it without training unlike Inuyasha who takes a lot of effort to wield it. Despite his actions, he is easily forgiven but unlike Koga he never opens to the cast at first. Then he gains God Mode powers which allow him to grow a new arm, comes armed with a sword that automatically heals him and even a technique that rivals The Hero.
Growing the Beard: Once Kikyou is revived, a much more complex and intricate plot arose from what had previous been fully a Monster of the Week story. While it strongly contains the previous elements, the story would focus more on the group facing a far more intimate enemy than they had previously faced.
Jerkass Woobie: Kagura, Inuyasha. The former is forced by Naraku to do his whims and only can be free on death, all she wants is to be independent and free. The latter, has his mother dying at a young age, hunted down by both demons and zealot, demon hating humans from that young age, his own half brother despises him, a malicious Big Bad forces his first love to betray each other and that's not even getting into the constant abuse from his allies, justified or not. It's no wonder he's very against everyone.
Kagome is Type B: Because she is the easiest character for a girl to relate to, she is paired up with tons of characters while the author projects themselves onto her.
For his part, Sesshoumaru is Type A: He is the most lusted-after male character, so girls usually pair him with a female character that they can relate to (usually Kagome) and project themselves onto the female as a sort of Wish Fulfillment fantasy of putting themselves with him.
Les Yay: Episode 98. "Kikyou and Kagome: Alone in a Cave", focuses on the two putting aside their differences for once and working together to survive. The episode title alone sounds precisely like a fanfic prompt.
Like You Would Really Do It: To no one's surprise, our heroes were able to get the Sacred Jewel shard out of Kohaku's body without killing him.
Magnificent Bastard: Naraku, especially by the Band of Seven Arc, when he managed to get both Hakushin, a holy priest and the entire Band of Seven to serve him with a few good choices of words.
OSUWARI/SIT! In actuality, Kagome uses the control collar less and less over the series, not every time he says something off. It's also more played up in the anime than the manga, as she mostly stops using it the way she did earlier on around volume 7 or so.
Sango slapping Miroku for groping her. She stops slapping him after he proposes, which happens almost halfway through the story.
Naraku crosses it when he breaks up InuYasha and Kikyou, which leads the former to being pinned on a tree for 50 years and the latter to her death, as well as putting a curse on Miroku's family that slowly destroys them; and that's before he's even properly introduced. And once he is introduced, it's really hard to pick when he crosses in the main story, things like turning Kohaku into a Tyke Bomb to kill his own family and then uses that guilt to make him do his bidding, landing a mortal wound on Kikyo at Mt. Hakurei, having Kagura and Kanna killed because he had no more use for them, trying to have Kagome kill Inuyasha the same way Kikyo sealed Inuyasha and killing those allied with him once they served their use. It is taken even further by the anime, where he really crosses the line between The Corrupter and Evil Genius into an utter monster when it's revealed that 15 years ago he tried to kill a young priestess named Hitomiko just because of the small possibility she might pose a threat.
Taigokumaru, a nasty bat yokai who manipulates his own granddaughter to do his bidding crosses it when he revealed murdered his own son for fraternizing with a human.
Goshinki crosses it when he gloats about killing two orphaned village children about killing their parents.
Renkotsu when he kills Jakotsu to get his Jewel Shard.
Moryomaru when he gloats about Kagura's death.
Gantenmaru and his men cross it when the former drains women's essence in front of Inuyasha and the latter cross it when they still help their boss even after he's revealed to be a blood sucking demon.
Narm: The dog demon forms of Sesshomaru and his and Inuyasha's father can come off as more cute than scary due to the rather feminine-looking dog ears.
Nightmare Retardant: While the manga is good at producing frightening demons Magatsuhi's true face is more Narmy than actually scary.
One-Scene Wonder: Due to the long nature of the series, several characters whose prominence is in one arc and never appear again are this, including an old exorcist woman from the Demon head arc, several possible Ship Tease interests and a great deal of demons and villains whose traits are as or more so interesting than the main villain and his overall scheme; most particularly the Band of Seven
Kagome and Kikyou both come in for quite a bit of hate from different ends of the fandom, most of it grounded in their mutually exclusive cases of Die for Our Ship.
Likewise Shipo, as a mouthy tagalong kid, and Koga, whose appearances inevitably touch of friction between Inuyasha and Kagome and whose introduction into the series leaves a shadow of Protagonist-Centered Morality over his subsequent characterization that makes him hard for some fans to accept.
Hojo, for his inability to catch a hint that Kagome isn't interested in him.
Ship-to-Ship Combat: The Kikyou/Inuyasha and Kagome/Inuyasha shippers hate each other, and if they were given the chance they would take up arms and start physically fighting. Then the shippers for any of those three with Koga, Sesshomaru, Rin and/or Kagura (or any of those four with one of the other three) would get pulled into it for one side or the other, and it would spiral out of a two-sided war into a multi-melee brawl. About the only shippers that wouldn't get involved are for Sango/Miroku, as the most official and least ambiguous of the series' pairings that isn't really a threat to other pairings nor do others threaten it...but there are periphery fandoms for pairings like Inuyasha/Sango and Miroku/Kagome. And let's not touch on the fandoms for Kagome with one of the Band of Seven, Koga or Inuyasha with Ayame, or any of the above with Naraku.
Some Anvils Need to Be Dropped: In-universe for Sesshoumaru: 1) Compassion is a good thing. 2) You don't need your brother's sword. 3) You are NOT infallible. 4) No, really. YOU DON'T NEED YOUR BROTHER'S SWORD.
They Wasted a Perfectly Good Plot: It's never explained why only Inuyasha can follow Kagome through time, which wastes some very interesting plots involving other characters and how they react to the present, especially with very dangerous characters like Naraku becoming a threat in the present rather than the Monster of the Week that occasionally shows up. Later justified as it is revealed in the first movie that the tree and the gateway that was made from it, were a sacred tree of time, so being bond to the tree, as well as being in close proximity to it is what allows Kagome and Inuyasha to travel through time. It's still a waste of a good idea though
The Inu no Taisho, the third film shows how much more powerful and wiser than both of his sons, while being entirely Badass as he was at his death thralls to save Inuyasha's mother. In his rescue attempt, he had used his two swords to mow down an army of soldiers and omniyoji with ease, revived Izayoi with the third, shot down with arrows and spent his last moments fighting a samurai in a collapsing buying castle. This is after suffering fatal wounds from a powerful lightning spewing dragon demon of the highest caliber that he barely managed to seal away.
It's very easy to mistake Shippo for a girl at first, in both anime and manga.
Sesshomaru is also very feminine looking and some mistake him for a woman.
Villain Sue: Naraku, thanks to the combination of his tendency to use puppets and lesser villains as pawns to accomplish his purposes and his talent for coming up with ways to escape beatdown after richly-deserved beatdown. Also for the fact that he has zero different sides to his personality and seems to be evil for no reason at all.
What an Idiot: Hey Kikyou, if the bad guy is unable to kill you, don't reveal it to him or you'll probably be thrown from a cliff... No, don't give him the jewel's fragments, you are only making him stronger!
What Measure Is a Non-Badass?: Fans throwing a fit because Sango dared to get married and have kids, and calling Kagome "weak" because being physically weak somehow makes you a weak person overall, even though she was just a regular schoolgirl thrust in the feudal world and she STILL gets a lot stronger as time goes on. It's averted in the actual series: Sango is a feminine, Yamato Nadeshiko family girl who is a demon slayer, and Kagura is a Lady of War that fights in a pretty kimono, her weapon is a pretty folding fan, and her attacks are all dances.