This usually is done either by an actual cutout in the character's outfit or a scalloped or notched hem in the character's top that combines with their pants/shorts/etc. to frame their navel.
Compare with Navel Outline, where a character's navel is covered but still apparent through her clothing.
Contrast Bare Your Midriff, where the midsection is largely or fully exposed. A lot of characters' costumes have belly-baring openings in them; to fit this trope, the character must be able to mostly or completely cover the area exposed with one hand.
- Blood Blockade Battlefront: Of the two female members of Libra, Chain's shirt and suitcoat are figure-hugging but otherwise unrevealing, while K.K. wears a short shirt and low-riding shorts covered by a long overcoat which is mostly unfastened and leaves her navel exposed.
- Don't Toy With Me, Miss Nagatoro: Nagatoro's "demon king" guise, which she appears to Senpai as in ch. 9 and which he imagines her as when she offers for him to sit with her and her friends in the school cafeteria, is a collared leotard with a devil tail and a heart-shaped cutout framing her navel. In the latter scene, this outfit is actually more modest than the devil getup Senpai imagines one of Nagatoro's friends wearing. The heart imagery also is a visual cue to Nagatoro's feelings toward Sempai.
- How Heavy Are the Dumbbells You Lift?: One of Satomi Tachibana's cosplay outfits is a skintight catsuit that sports a diamond-shaped hole exposing her navel, which left a tan mark that her students quickly took notice of.
- Little Witch Academia: Shiny Chariot's white jacket combines a roughly figure eight-shaped navel cutout and a plunging neckline, ostensibly to draw even more attention during her public performances.
- Maho Girls Pretty Cure!: Cure Miracle's Sapphire Style form has a flared notch in the upper garment which only exposes her navel, contrasted with Cure Magical whose Sapphire Style features a halter top with a sari-like extra garment over it.
- Karin's lab coat is cut out to show a portion of her stomach
- The qipao-style dress Sakura wears in adulthood splits just high enough above her pants to leave her navel visible.
- Neon Genesis Evangelion: At one point, Asuka wears a jumper-like outfit whose top has a notch in the hem that shows her navel. This isn't the first time she's worn anything revealing around Shinji, but in this instance, the reduced exposure fits with the mood of the scene, as she's asking Shinji if he's talked to Kaji lately and is dejected when he says he hasn't. This contrasts with an earlier conversation between them when Asuka is at her most confident and psychologically stable and is wearing a tube top and shorts.
- Harley likes to wear an outfit which makes him resemble his Cacturne, which includes both a vest with Cacturne's pattern of diamond-shaped dark spots and a shirt with a diamond-shaped cutout around his navel.
- Marian from the Sinnoh saga wears a long sleeveless top which splits in the front just below her breasts, creating a triangular opening that shows her navel.
- Puella Magi Madoka Magica:
- Sayaka Miki's Magical Girl outfit features a white corset with a gap around her navel, which exposes her soul gem.
- Kyoko Sakura doesn't attend a school like Madoka and her friends and has a snarky, rough-and-tumble personality. In keeping with this, her casual clothes are short shorts and a jacket over what is likely some kind of belly shirt, as the jacket is unfastened at the bottom just enough to expose her navel.
- Puella Magi Tart Magica: Corbeau features a cutout in her outfit around her navel that vaguely resembles the nib of a fountain pen.
- Yatterman: The 2008 remake ups the fanservice value of Hiroko Sasagawa's outfit by giving it a diamond-shaped opening showing her navel.
- In the promotional image for Avenging Angel, Angel's Street Walker garb features a zip-up shirt with an angled hem that exposes her navel.
- Vocaloid Megurine Luka has this in both her original and V4x designs. Both Kagamine Rin and Len (the latter a Rare Male Example) also have this in their Append designs. Another Rare Male Example would be Kaito, but mostly just in his default (and thus as close to canon as you can get) MikuMikuDance model. Most fanmade models and canon artwork of him depict him as wearing a shirt under his coat.
- Atelier Ryza: Ever Darkness & the Secret Hideout: Ryza's shirt has a convenient cut on the lower half of her shirt that seems to have no purpose other than expose her navel. Even after becoming a full Alchemist and gaining a belt, the belt still doesn't cover her navel.
- Grimms Notes: The dress worn by Lira's Essence combines this with Absolute Cleavage, as the small oval slit that shows her navel starts where the opening in front that shows off her cleavage ends.
- Honkai Impact 3rd:
- Rita Rossweisse's Maid of Celestia outfit is an elaborately designed cheongsam which, among its many fanservice aspects, has a diamond-shaped cutout around her navel. With most versions of Rita, her default "waiting" pose is to stand with her hands resting crossed on her belly; in this outfit, this stance puts her hands directly over the cutout, almost as if she's trying to hide it.
- While Raiden Mei has several revealing outfits, the only ones that actually expose her navel are her default as the Herscherr of Thunder and Orochi Cutlass, an alternate outfit for her Shadow Dash battlesuit which closely resembles the previous one. In both of these, said exposure is via a small diamond-shaped cutout with her navel just visible at the top corner.
- Bronya Zaychik's default outfit as the Herscherr of Reason has a roughly diamond-shaped opening that, in her character sprite, shows the upped cleft of her navel but doesn't fully expose it, while artwork goes back and forth on whether it's covered or exposed.
- The most fanservicey piece of the Beethoven Stigmata set features her lying on her back with her shirt partially untucked and unbuttoned just enough to show her navel.
- Pokémon has two inversions:
- Elesa's outfit in Pokémon Black 2 and White 2, which has her midriff bared except for a gray strip over her navel.
- Wallace's outfit in Pokémon Omega Ruby and Alpha Sapphire, which shows his midriff except for a diamond commected by two straps covering his navel. His midsection is less bared than Elesa's above.
- Street Fighter V: Menat's story mode outfit, which is the least revealing of the three she has, still features a half-moon-like navel cutout.
- Fire Emblem: Three Houses: The female version of Byleth ups the fanservice from the male version by creating such a gap via both an angled hem on her top and a notch in the top of her extremely short shorts.
- Kingdom Hearts II gives a few rare instances of a male version of this trope. Setzer and Riku both wear button or zip up undershirts with the bottom of the shirt undone, which flashes their navels.
- RWBY: Blake's outfit in Volumes 1-3 features this, but due to a software error her model doesn't have a visible belly button. After Volume 4 (and a change in animation software), her outfits trend toward a more traditional Bare Your Midriff style, but flashbacks done with the new software featuring the old outfit now show her belly button.
- Steven Universe: Rose Quartz most often wears a long white dress with a star-shaped window around her navel, which exposes her gem.
- Futurama: Leela's swimsuits often feature cutouts over her navel. Her workout leotard in "Jurassic Bark" has further cutouts on the side to show off more of her stomach.