To cultivate creative talent, ways to learn creative problem-solving skills is needed, and one of them is programming. Arduino is a well-known tool used for programming education and the usefulness has been demonstrated in various case studies. However, there are several problems in existing Arduino-compatible kits as education tools, including the need for understanding hardware and the difficulty of expanding the kits with third-party hardware. In this paper, the design of an Arduino-compatible modular kit, called as FRUTO, is proposed that can be easily connected and conveniently programmed to overcome the problems. The structure and features of the FRUTO kit that implements the proposed design are also shown. The FRUTO kit consists of the FRUTO module that uses a unified connector for easy and intuitive connection and the FRUTO library that abstracts hardware-dependent code for easy programming. The FRUTO kit is easier to use and more scalable than existing kits. Even more, it can be used in various ways depending on the students' familiarity with hardware and programming. These strengths will make the kit to be an appropriate tool for various microcontroller-related education as well as programming education.