Shonen Upgrade is a common trope in, well, {{Shonen}} series. It's an item, power, or transformation gained by a main character to drastically increase their abilities. Most commonly it's some sort of "special ability" or "new move," like a SuperMode. It sometimes appears as an EleventhHourSuperpower, a DangerousForbiddenTechnique, or, rarely, IAmNotLeftHanded.

The ShonenUpgrade usually doesn't involve "just" training, no matter how [[TrainingFromHell hellish]] it may be; there's always some exterior source for the power, like a magic weapon, an [[LifeEnergy infusion]] of ''[[KiAttacks ki]]'', or a TransformationRay. Many of the more powerful {{Shonen Upgrade}}s have some sort of [[PowerAtAPrice downside]] attached, such as risk of a HeroicRROD ([[DeadlyUpgrade if]] [[PowerDegeneration not]] [[TheCorruption worse]]) if used too much, or a risk of [[SuperpoweredEvilSide losing yourself]] to TheDarkSide.

See also NewPowersAsThePlotDemands. In [[HumongousMecha Mecha Series]], the equivalent is the MidSeasonUpgrade.
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!!Examples:
* The most well known example of this trope is the various levels of Super Saiyan from ''DragonBallZ'', though early on there was a previous ShonenUpgrade in the form of the Kaioken, which increased Goku's power at the cost of [[HeroicRROD the toll it would take on his body]] [[DangerousForbiddenTechnique if he used it at too high an intensity]], as well as a later ShonenUpgrade during the Majin Buu saga in the form of Fusions.
* The most well known example from live action TV is the conversion of the ''PowerRangers''' [[HumongousMecha Dinozords]] to the new Thunderzords.
* Most of the ''OnePiece'' characters gained a new weapon, tool, or power in the Skypeia arc.
** Specifically, Zoro gained a RazorWind attack and Nami got a Jet Ski. The real upgrader was the [=CP9=] Arc, when Luffy gained two new forms, Chopper gained a SuperpoweredEvilSide of sorts, Nami upgraded her previous weapon, Usopp became a superhero, Sanji set his attacks on fire, and Zoro tripled his swords to nine.
* Shinigami in ''{{Bleach}}'' have 3 forms to their Zanpakuto, "Unreleased", "Shikai", and "Bankai". Ichigo starts out with just a basic "unreleased" sword, and gains Shikai, and later Bankai, through pure ShonenUpgrade moments. In addition, Ichigo's Hollow powers are a similar example, powers acquired, not through training, but by dramatic need.
** Some of other main characters (Rukia, Chad, and Uryuu) have received upgrades, as well. Renji is a bit of a subversion, as he hasn't upgraded since his initial HeelFaceTurn upgrade. Orihime hasn't really received any upgrades throughout the course of the series, except for the fact that her [[CallingYourAttacks attack calls]] have been shortened.
* In ''{{Naruto}}'', the title character's Kyuubi tails are a form of this, as is the forming of Sasuke Uchiha's Sharingan mid-fight-scene. Choji Akamichi's special Food Pills also count. There is also Orochimaru's Curse Seal, which Kimimaro, the Sound Four, and Sasuke all have. Kankuro gains more Ninja Puppets, while Tenten gets Weapon Scrolls. Later on, there is Jiraya and [[spoiler: Naruto ''again'']] with Sage Mode. And, of course, Rock Lee and Might Guy have the Eight Gates to move up through. [[CaptainObvious Naruto uses the trope a lot]].
* ''BoboboBoBoBobo'' 's Shonen Upgrades are direct parodies of ''Dragonball Z'''s Super Saiyan and Fusions.
* In ''{{Yu-Gi-Oh}}!'', the God Cards are a version of this. So are the Orichalcos arc Legendary Dragon cards, which were brought into the main character's deck by pure willpower and TheMagicPokerEquation. The cards ''didn't actually exist'' before the moment the main character needed them and they magically came into existence. In ''{{Yu-Gi-Oh GX}}'', Judai/Jaden's Elemental Hero Neos and the Neos Fusions count too.
* In ''{{S-Cry-ed}}'', Kazuma goes out to upgrade his Alter power because it is too weak, then later gets an additional upgrade at the end of the series through willpower. Ryuho also follows this, but his first upgrade is more an IAmNotLeftHanded, in that he had it retroactively.
* In ''{{Guyver}}'' there is the Gigantic upgrade for each character equipped with a Guyver. Only problem there is a limit on using it and is essentially a suit that can be worn by only one character at a time. Aptom himself can qualify in which he slowly gains more power by absorbing more Zoanoid types.
** Guyver I can take the Gigantic upgrade a step further by transforming into the Gigantic Exceed, an [[HumongousMecha apartment-sized bio-armor]]. He's used it once so far, to fight the Zoalord Kabarl Khan in his equally huge zoanoid form.
* ''MahouSenseiNegima'' has several of these. Several characters are half-demons with superpowered demon forms to match. Anyone with a Pactio can supercharge their strength with magic as well as summon a powerful artifact. Negi himself has his BlackMagic. [[spoiler: Not to mention his own Pactio]].
** After being defeated in her rematch with Tsukiyomi, Setsuna eventually gets one of these in the Magic World arc [[spoiler:via her new Pactio formed with Konoka, which granted her a different Pactio Card than the one she got from Negi]].
* In ''SaintSeiya'', the Sacred Cloths of Athena change into sleeker, more impressive new forms whenever they're destroyed and have to be rebuilt (especially the Bronze Cloths, which are broken at least once per series.) Works as a non-sexual form of {{Fanservice}} as the Constellation form of the Cloths [[CostumePorn becomes more and more intricately detailed with each iteration]] -- the original Pegasus and Cygnus Cloths required a LOT of imagination to resemble a winged horse or a swan, but by the time they became [[spoiler:Divine Cloths through [[ShonenUpgrade Athena's blood]]]] they were near-perfect reproductions -- and they cover more and more of their Saint's body at the same time.
** In regards to the Saints themselves, their goal in the Sanctuary Arc was to awaken to the mystical [[EleventhHourSuperpower Seventh Sense]], which would allow them to perceive the [[BattleAura Cosmo]] of faster-than-light Gold Saints and counterattack. In the [[BigBad Hades]] Arc, the objective was the ''[[NewPowersAsThePlotDemands Eighth]] Sense'', which grants them entrance into [[{{Hell}} the Hades]] while still being alive. Then, when facing Hades' [[TheDragon Dragons, Thanatos and Hypnos]], the overwhelming force of the Bronze Saints' Cosmo upgrades them (and their Cloths, see above) [[AGodAmI to godly levels]].
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