It has been reported that the introduction of ferromagnetism by various ways into topological insulators (TIs) can induce concerted effects, resulting in various novel magnetic phenomena such as quantum anomalous Hall effect and skyrmions. In addition, recently, efforts to increase the observation temperature of quantum phenomena by enhancing the crystal quality and improving electronic coherence have been pursued with great enthusiasm. Self-assembled regular alloy crystals such as Mn(Bi,Sb)2Se(Te)4 are called “intrinsic” ferromagnetic TIs that have recently attracted much attention, and we have observed skyrmions in sandwich structures based on these crystals. Furthermore, we have newly observed the ferromagnetic proximity effect even at room temperature at the heterojunction interface between Fe and topological crystalline insulator SnTe by polarized neutron reflectometry. As an extension of these efforts, it is hoped that the unique properties of TIs will be utilized to develop next-generation robust devices for such as spintronics and quantum computing.