TA恋心 is a personalization app that allows you to change the display typeface on your Android device. Developed by SHARP CORPORATION, this app offers a variety of downloadable fonts, including the handwritten typeface "TA Koishin," which is free to use. With this app, you can easily change the display typeface according to your mood or preference.

One thing to note is that depending on the characters you use, such as "Heart" and "Hangul," the default font of your device will be displayed. In such cases, you can use a character input application like Google Korean IME. It's also important to mention that this app may not be available on models that do not support the download font function released in the fall of 2011 or later.

Overall, TA恋心 is a handy app for those who want to customize the display typeface on their Android devices. It's easy to use, and with its variety of downloadable fonts, you can find the perfect typeface to match your mood or style.