Kikyo, the tragic miko (shrine maiden) of Inuyasha, is something of a legend within the story’s canon, leaving behind a powerful legacy even protagonist Kagome has trouble upholding. Along with being one of the more powerful miko who ever lived, Kikyo is especially remembered for her tragic downfall by falling in love with Inuyasha.
At first, it may seem strange that love would be the thing to destroy Kikyo, especially considering the same didn't happen to Kagome. But there's really no comparison for one simple but significant reason: Kikyo is a historical miko and Kagome is not. While Kagome may have inherited Kikyo’s spiritual powers and kyūdō skills as her reincarnation, she's also a woman of her time and was never subjected to any of Kikyo's training for a miko living in Japan's Sengoku era.
Historically, Kikyo Began Her Miko Training In Childhood
Historically, miko in Japan fulfilled a very different role from their modern counterparts. While today's miko are seen assisting priests at Shinto shrines, in the past they were actually shaman women. As such, they maintained a position of power and authority within their respective communities. As practitioners of Shinto, their job description included performing divinations, exorcisms and communicating with the kami (spirits and deities) of their respective communities. That last one entailed allowing kami to possess their bodies and convey their messages through a trance-like dance that is performed today as kagura or miko mai.
Within Inuyasha canon, Kikyo is seen performing many functions of the historical miko, most notably exorcisms with her asuza yumi (sacred bow) and hama ya (exorcism arrows). To become a miko, however, Kikyo couldn't just be anyone. She either had to be the daughter of a shaman or had to possess strong spiritual potential. While nothing is known about Kikyo's parents, she does, have a reputation for immense spiritual strength. That power is most likely how she got selected by her community to train to become a miko.
Per Japan's own history, to become a miko, Kikyo would've begun training at a very young age and undergone a series of purification rituals. Since training lasted anywhere from three to seven years, Kikyo would've started her training at age 10 or 11 if she was approximately 17 or 18 at the time she met Inuyasha. The completion of her training would've ended with a ceremony to symbolize her bond with the kami Kikyo would commit to serving, which was the reason she had to remain a virgin. Since purity is central to the Shinto belief system, maintaining sexual purity was essential to Kikyo fulfilling her role as a medium for her community's kami.
Being A Miko Was At Odds With Kikyo's Humanity
Despite Kikyo's training paying off and establishing herself as one of the more powerful miko known throughout Japan, her life was also at odds with her humanity. Kikyo was more than aware of what she was sacrificing to fulfill her responsibilities to her community and the kami she vowed to serve. This internal conflict became a major source of unhappiness for Kikyo, who was still a teenaged girl, and was explored in detail in the Inuyasha anime spring special "Tragic Love Song of Destiny".
In the spring special, Kikyo's powers and talents another miko's envy -- Tsubaki, whom she trained with. At the start of the special, Tsubaki went out of her way to remind Kikyo of what her training entailed and why she couldn't fall in love with a man if she intended to maintain her spiritual strength. This was Tsubaki's no-so-underhanded way of reminding Kikyo how quickly she can lose all that she has worked hard for the moment she compromises her sexual purity. In fact, she was counting on that happening given Kikyo's youth.
While Kikyo brushed off Tsubaki's "advice" as placing a curse on her, it was established in both the Inuyasha manga and anime that -- as the more powerful miko of the two -- Tsubaki's curses don't have an effect on Kikyo. Still, Tsubaki wasn't off in her prediction given Kikyo's own internal conflict in reconciling her humanity with her miko existence. More than anything, this was the reason Kikyo refused to kill Inuyasha every time he pestered her for the Shikon no Tama (apart from recognizing he was a hanyō and not a full yōkai) and what led to her bonding with him.
Falling In Love Led To Kikyo's Sexual Awakening
Over the course of their friendship, Inuyasha and Kikyo developed mutual romantic feelings. This led to them spending more time together, and to Kikyo becoming more emotionally vulnerable. One thing Tsubaki noticed in her next encounter with Kikyo was how much her spiritual powers had weakened since meeting Inuyasha. She once again reminded her of what she was compromising by allowing herself to fall in love. This implies Kikyo started experiencing sexual desire, which Tsubaki then attempted to exploit by unleashing her famous snake curse. Though the attack was easily deflected, Tsubaki still was not wrong in her predictions.
Not long after this encounter, Kikyo began experiencing the full extent of what her romantic relationship with Inuyasha was costing her. She was becoming less powerful and effective in fights against yōkai, one of which resulted in the loss of her sister's eye in the anime. This forced Kikyo to make a decision: give up her life as a miko and become an ordinary woman, or give up her romantic relationship to regain her strength as a miko. She ended up choosing the former, which led to her proposing that Inuyasha use the Shikon no Tama to become human. If he did, the jewel could be purified while Kikyo could be relieved of her responsibilities to it. After some thought, Inuyasha accepted Kikyo's proposal, which led to their first kiss in the anime special.
Kikyo's Downfall Is Linked To Loss Of Sexual Purity
Although the kiss in the anime was depicted as an affirmation of Inuyasha and Kikyo's love for one another, when examined through Japan's historical context, it was even more significant than that. In Kikyo's time, people in Japan did not kiss as part of romantic expression, but as part of sexual interaction. Since Kikyo is a woman of her time with no knowledge of western European notions of love, this means that when she kissed Inuyasha on the boat dock, she was initiating a sexual encounter. This happened during the daytime and Inuyasha was later seen escorting Kikyo back to her village late at night.
While the anime does not detail what Inuyasha and Kikyo did during those in-between hours, plenty of contextual clues in the aftermath hint at them having engaged in sexual activity. The first clue was Kikyo not detecting Naraku's distinct aura when he visited her at the shrine disguised as Inuyasha. Since Kikyo is skilled at detecting different yōkai auras (and especially Naraku's distinct aura post-resurrection), this is a strong indicator of how much her spiritual powers weakened. This was confirmed by Naraku later on -- in both the Inuyasha manga and anime -- as the reason he was able to attack and kill Kikyo. Had he encountered her while she was still at peak spiritual strength, he would not have succeeded in his plan to tear both her and Inuyasha apart.
Revisiting the question of why Kikyo's powers diminished by falling in love when the same didn't happen to Kagome, it boils down to the fact Kikyo is a historical miko, whereas Kagome is a modern miko. As a historical miko, Kikyo was bound by the rules of her occupation, which at the time entailed maintaining sexual purity. Kagome, by contrast, is not bound by those same rules as modern miko in Japan are no longer required to remain sexually pure to assist priests at Shinto shrines. As a 20th century girl, this is the perspective Kagome brings to the Sengoku era.
