Naruto gets this appearance after he filters kurama's mind from kurama's chakra
a portion in bijuu chakra mode
all of it in Bijuu mode
naruto has a strong yang chakra already because he inherited kushina's life-force=yang
Minato set naruto's seal up for his chakra to mix with kurama's chakra which is the yang half
This is what made Naruto have that appearance that he has when his chakra is combined with kurama's
Kishi was influenced by the mythology Legend of the bijuus,and it says the reason why the kyuubi was so strong was because of his Fire Seal
yang represents fire and yang represents the senjus;they inherited the sage's life-force and physical energies making them have a yang chakraTale in the Legend of the Tailed Beasts: This is a Bijuu in the shape of a nine-tailed fox, and the strongest of them all. The reason he is so powerful is simple: Kyuubi has an unlimited amount of power, earning it the “King of Bijuu” title. The power is generated by Kyuubi’s Fire Seal, and as a result, after battling for 100 years with Yamata no Orochi, it becomes exhausted; but Kyuubi continues standing, able to fight. It is also pretty cunning and smart.
Situation in the Ancient War of the 9 Gods: Battled 4 times; All of them victories
Wins: Nekomata, Houkou, Raijuu, Yamata no Orochi
Fate: In unclear whereabouts, Kyuubi continues to kill all the people on his way to find the one who awakened him, and the one who managed to seal him before.
Myth Appearance: Kyuubi no Youko is the strongest Bijuu of the Japanese Myth. Its body has a red fur; Kyuubi represents the element of Fire. Its abilities are incredible. Because it has never been defeated, its total strength is unable to estimate. His tails create cyclones by spinning quickly, and Kyuubi proceeds to rip its enemies with its huge claws. At the same time his fur may shoot fireballs similar to meteorites endlessly, instantly destroying villages. In the ancient Bijuu wars, a challenge results in Houkou being severely wounded, and Nekomata nearly dying, The Kyuubi is an intelligent bijuu and has a scathing, sadistic personality. However he has also a sense of fairness and sarcastic honour.
naruto also looks like he's on fire when he uses kurama's yang
the younger son has a flame-like chakra pattern
senju's will of fire and obito can tell it dwells within naruto
the more naruto gets kurama's yang and it mixes with his the more his chakra signature is like the younger son
the sage invented a seal for the juubi and it's being quietly passed down
the sage had a yin and yang chakra so his seal looked like this;the same with obito he's hashi(yang)and uchiha,but has mangekyou instead of ems that might be why that horns bigger and seals different
he passed it down to his younger son but his younger son only had a yang chakra;the seal with only yang(fire)=fire seal;and eventually the uzumaki's only knew how to perform the seal,Kushina taught it to minato.
Minato didn't use the eight tri-gram seal to combine his chakra with yin kurama neither did he have time to separate the mind from the chakra;if he uses kurama's chakra he should look like kinkaku and ginkaku
or killer bee
Minato is a senju and has a strong yang chakra, but only as strong as naruto has when naruto's chakra is mixed with bijuu chakra mode naruto, and used the Fire seal;that's why he hasn't used chakra arms for his missing arm.
Hashi represents the younger son and has as much chakra as naruto and kuramas chakra,if he does the Fire seal he will have the same form as bijuu mode naruto.
in the last manga when minato went into bijuu mode his appearance didn't change like naruto's did, the only change was his eyes,that's because his chakra isn't combined with kurama's yin chakra
he's using a bijuu mode more like killer bee's where the chakra doesnt mix
Minato gave naruto the eight tri-gram seal and kurama's yang hoping he would blaze(fire) the trail to the future