Kokoro no Senshi was intended to provide an introduction to Angela Aki's style to Square Enix music fanatics prior to the release of her Final Fantasy XII single. Featuring an arrangement of "Eyes on Me," Nobuo Uematsu's famous main theme from Final Fantasy VIII, this song's widespread popularity from gamers was a commercial ploy to attract people both to this single and the subsequent one. Even though its inclusion and arrangement are dubious, the experience is heightened by three original themes, including the title track, "Kokoro no Senshi," aka "Warrior of the Heart," ultimately satisfying most of those who didn't just come to hear another "Eyes on Me" rendition.
Starting off with the title track, most would anticipate "Kokoro no Senshi," aka "Warrior of the Heart," to be dazzling and musically impressive, though it suffers somewhat from being unbalanced. The introduction to the theme is perhaps its worst feature; opening with a single piano chord, Aki sings unaccompanied until a sudden pile of violins and drums enter in a way that is jarring. The verse section following the introduction is simplistic yet endearing, enhanced by Angela Aki's sensitive vocal and piano performance, both of which are emphasized throughout, while other instruments are absent. Unfortunately, Shin Kono's string arrangement for the Ittetsu Gen ensemble hinders the track once more as it abruptly builds into a sweeping, mesmeric, though undoubtedly inappropriate chorus section. Still, even though the track does suffer greatly from poor instrumental balance, Aki certainly puts her heart into the theme and the melodies are rich, meaning it otherwise suffices as a mature Indie song.
"The Sky Is Always Crying" is far more upbeat and well-structured than "Kokoro no Senshi," combining strength with simplicity. The piano line remains simple for the first section of the theme, and with Aki's voice buoyantly gliding around its warm tones, the introduction of a guitar doesn't seem out of place at all. The verse section allows Aki to freely manipulate the vocal melody and demonstrate the versatility of her voice while accompanied by just a harmonically simple yet solid and steady piano line. The transition into the chorus section is made smooth by the crescendo that occurs in the piano line, as the guitar and drums enter once more. Indeed, though the structure is rather similar, it is contrasted by superior instrumental balance, more positivity, a waltz-like rhythm, and rich dynamic variety, ensuring its accessibility is greater and its presentation is refined. The result is an excellent and very fun track.
"Today" is a powerful track that features Angela Aki's vocal performance with just a piano accompaniment. Unlike in "Kokoro no Senshi," where the piano and vocal line seemed bare in places, immediate atmosphere is created that enhances the captivating energy that radiates from the track as a simple yet potentially effective combination of forces is utilised. It does so much from so little, with Aki's performance, which emphasises the meaningful lyrics with accentuation, dynamics, and other decoration, being the leading feature once again. Still, it fails in certain respects, never quite developing to reach its full potential; no matter how much the vocalist pours her heart into the performance, somehow the piano line never quite manages to touch in the same way, feeling awkward and harsh in places, almost entirely chordal and not performed with much compassion. The piano line may be what offers Aki all of the inspiration for the passion that she pours into her vocal line, but it is also the reason why she has to try so hard.
The single concludes with an arrangement of Nobuo Uematsu's "Eyes on Me" from Final Fantasy VIII, originally sung by Faye Wong, and now sung by Ms. Aki herself. It is probably one of few reasons why a Final Fantasy fan may consider buying the album, but it is likely that many will find it disappointing, as it is not as outwardly beautiful and balanced as the original theme nor as sophisticated and elegant as the orchestral version featured in the "Ending Theme" of the Final Fantasy VIII Original Soundtrack. An arrangement for piano and voice, just like "Today," while the piano line supports Aki's voice well and integrates some pleasant jazz-oriented features, it feels too minimal; inappropriately placed fortissimi and excessive accentuation fail to enhance the emotional power to the level most would expect. Aki's performance is upbeat, light, and carefree, which results in an interesting variation, complemented effectively by the dynamic and vocal range of her voice, accurate interpretation of the English lyrics (she's bilingual, after all), and overall impressive display of musicianship. Still, this isn't the "Eyes on Me" most would expect and it will disappoint those expecting a heartfelt or harmonically rich variation.
Ironically, the centrepieces of Kokoro no Senshi, "Eyes on Me" and the title track, were the disappointments, while "Today" and "The Sky Is Always Crying" proved much more balanced and enjoyable. Unfortunately, this significantly reduces the target audience of the single, as those Final Fantasy fans that loved the original "Eyes on Me" may not enjoy the arrangement of it here, the weakest track. Nonetheless, for those who enjoyed the now-released and superior "Kiss Me Good-Bye" single, this single may be worth considering, as its middle tracks are of similar quality to the non-FFXII tracks featured there and should be very appealing to practically all fans of mature Indie pop that listen to them.