It honestly depends on the message you think Satsuki is trying to convey. I honestly like both lines, as I think they both pertain to her character. Building it in her mind does exactly what you say-gives the impression that despite being a 5 year old, she's incredibly more mature than anyone else. She has mental fortitude and resolve, and will accomplish what she wants with resolute power.
**MAJOR SPOILERS**
Building it in her heart hints at her true self-that she is more emotionally driven than the viewer first believes. Her genuine love for a sister she never knew, as well as her father who she barely knew, is what drives her to do what she does. A skyscraper in her heart means that Satsuki will take revenge for a love that she never had to opportunity to have. In the end, it comes down to what aspect of Satsuki you want to focus on. Do you want to highlight her maturity? That's totally fine. Do you want to foreshadow her real feelings? That's totally fine too. But saying there's literally nothing good about the line is very close-minded.
Clorox-neesan
2018-11-20 20:19:22 +0000 UTC
Right, almost like a regular 5 year old, except for the little detail of her knowing exactly what she wants to do with her life better than the typical 30 year old...
Bingbong
2018-11-19 00:24:09 +0000 UTC
but thats the thing, shes not supposed to be like a 5 year old, shes basically supposed to be a god in terms of maturity levels. The dub censors her basically and makes her sound like a kid, thats bad, literally nothing good about that.
uwu owo
2018-11-18 21:50:06 +0000 UTC
I like the dub version of the kindergarten scene, there Satsuki says you should "build the sand castle in your heart", which sounds way more like something a 5 year old would say.